Understanding Battery Life...
Something people need to understand a little with battery life and those nags people get about phones.
First off - Out of the Box Battery Life - I am sure many of you remember that the rep and even some manuals say you should 'charge your battery for 24 hours before using'. This is roughly 'conditioning the battery'. By Law, devices are not suppose to be shipped with the battery installed. And more to the point, the battery is not to be at 'full charge'. The reason for the message of needing to charge the battery for 24 hours is to insure it has a good standing charge and to get the most out of the battery as much as possible.
What most people don't do, and I am also one who has done it with my own droid, is assume that we have a good battery and just use it. Problem is, most batteries do not function in a 'linear' way. Linear meaning, I go 5 steps, it is 5 steps down, I go another 5 steps, it is another 5 steps down.
Most batteries function in a logrhytmic way. Logrhythmic, meaning that I go 5 steps, it will go down 2, I go another 5 steps, it may go down 3, another 5, it may go down to 3.5. It isn't steady or 'straightforward'.
Standby/Talk time - People wonder why there are two different times, and yes, I know many of you know standby means phone isn't being used, and Talk is when it is. What people don't understand is why the battery can't maintain both at the time.
Standby is longer due to the fact that you are not broadcasting. Broadcasting a signal, even with towers trying to receive signals, still takes a reasonable amount of power for a device of its size. The power to just 'listen' for a "Hey, you got a call/text" is minute mostly because you just need to receive a signal and process it. But when talking or making a call, you are not only receiving and processing the signal, but also trying to send out a message back out and hoping another tower will receive and process it. If these were the old Analog phones, the ones with the big battery packs and huge antennas, you would be using a lot more power to do the same thing.
Apps - As many people here have stated, you really don't need to go Kill App crazy, however, you do need to understand something with regards to some apps.
Any app that needs to use the network, will cause a slight drain in the battery. Why? Well, let's explain something about how the internet works.
Network Apps need to 'talk' to something. They send data to a server saying, "Hey, give me data for this..." So now, you are spending a little 'talk time' because your phone is sending a signal out due to that app.
Things like Streaming Music, IM, or even that little weather update app you have running. They will go "Hey, I need more info, send it to me." So you are burning battery power because these chatty programs are sending data out to get more data in.
This is the reason why one of the battery conservation suggestions from the droid booklet says to not have background data or sync on all the time. While Gmail can push its mail, the pop/imap stuff will require you to setup a time interval so you can get your mail, but generally, you want it at a longer time interval to avoid constant 'chatter'.
And just so you know, IM is one of those constant chatter apps because it does ping the IM Server with the "I'm online" status. Most IM programs don't have a convenient 'sync' timer to do that, as IM servers and clients like to keep 'up to date' on status for that reason.
This is not to say you need to go crazy or OCD on killing tasks, just be aware that if you want to prolong your battery life, make sure you minimize the number of network talking apps as much as possible. The fewer there are, the less 'talk time' is used on the battery charge.
Some battery life comments....
I work in electronics with batteries myself, so I figured I'd add a few comments.
Most companies do suggest you charge for 24 hours on start. Part of that's the fact that Li-ion cells (unlike NiMh or NiCAD) have a fairly complex charging cycle... they like constant voltage during part of the charging cycle, then constant current. You don't worry too much, since the charging circuit itself is on your phone... but they want to ensure you get a proper charge.
In the box, the cell could have bleeded power. Li-ion cells have a pretty low self-discharge rate, but when they drop too low, bad news... that can actually damage the cell. Really smart chargers know how to "reform" the cell, but that takes awhile. So they're just being very careful here.
On standby vs. talk... any time your phone needs to talk to the cell tower, it's putting out a power level that can reach up to 1 Watt of power. To receive a signal, you're talking a couple of milli-watts.. same reason you can run a Walkman-style radio off a couple of AA cells for many days. When you're in standby mode, the phone has to sync with the nearest cell tower, and may occasionally ping it from time to time, but this is very low duty cycle. In talk mode, any time you're talking, you are using the maximum power consumption possible on the phone.
App killing.. maybe a good idea, depending on the app. An app in the "background", not doing anything, will not consume any measurable amount of power. But not every app that's not up-front will not use power (or, applying DeMorgan's theorem, apps in the background can still suck power). Those on the network, sure, but any use of hardware can be a problem. I left one of those "GPS Status" apps in the background, and it was not written to go to sleep when not "on top"... it sucked down enough power to make the DROID warm, and kill the battery. Apple's big claim about not supporting application-level multitasking is "battery life". While suspect some of that isn't the reason (eg, they want Apple-provided apps to be in a different capabilities class than 3rd Party apps... in Android, anything Google can do, you can do, app-wise), they do have a point. Multitasking is a great tool, but so is a scalpel... great for a surgeon, but don't hand one to a fool. My point... watch your power hungry apps, and if you discover one, kill it, erase it, or get an app manager that will kill it for you once it's pushed to the background.
Another battery thing -- battery life, long-term. One of my big problems with the iPhone (and there were many) was the fact that, if you're a heavy-duty smartphone user, you probably recharge every night, and may often run out of juice before the end of the day. The iPhone had a cell that will give you 300-500 full recharges before it's dying fast and needs to be replaced. Which is big bucks, since you can't do this, only Apple. Most Li-ion technologies also fail over time, no matter how many cycles the go through, but that's more of a 3-4 year thing. Failing on the phone contract, though, that hurts.
But hey, Hybrid cars don't have this problem. I have a 2003 Prius with 120,000 miles on it... the battery gets charged and discharged every time I drive, how come it's still good? Well, it's NiMh, but more specifically, the battery never gets fully charged or discharged. In that year, they only run it past 40% of it's capacity... stop charging at 80%, don't use the battery past 40%, and it lasts really long. This seems to be true of Li-ion too.
So, unlike NiCAD, there's no memory effect. But better still, if you charge regularly, before the battery dies, it's likely to last longer than those 300-500 cycles, which are based on full cycling the battery. This is the reason the iPod folks are not up in arms about failing batteries... most people will charge every night, but most batteries will probably be at 30-50%, not 1%.