now this is weird, my phone is in the leather side pouch on my pocket and i could feel its warming up so i took it out and it is warm.. its like i used the browser for 20 minutes. i checked and apps were closed..
Screen brightness is a huge factor. My phone was on fire when i figured out how to crank the brightness up (and the battery life went way down). Turning the brightness down helped cool it off and save some battery.
Ok... keep in mind, some people say "phone", but what you really have here is a pocket computer with radio network.
The power of today's ARMs, why few other CPUs are in this niche, is do to low power per MIPS, but also very good power management. When the CPU isn't working hard, it's not sucking much power. But when it does work hard, yeah, you'll get a little heat.
Radio is likewise... cell towers tell the phone how good they're getting the phone's signal, and whether to boost it or not. At peak, most phones can put out 1/2-1W when transmitting... that's pretty serious, and will also yield heat, if you're doing enough transmitting. I don't know if EDGE/x1 is necessarily more power hungry than EvDO, but it's likely in most places, if you're not getting EvDO, you're just too far... it needs that high power output just to get the 1x link working.
I'm sure it'll be repeated constantly, but do be careful about the stuff that's running. Android keeps the last six apps running, unless it needs the resources. Well behaved ones sit on the idle queue, waiting for input, and don't consumer power. Bad ones keep sucking power. If you ever find your DROID is warm in your pocket after not being used interactively for awhile, you can bet you have one or more of these still active.