Picked up a Samsung Stratosphere a couple days ago, been playing with this phone quite a bit. I've installed all my regular apps, run it to dead and back to full a number of times (conditioning the battery) and taken it around town to try it out.
HQ YouTube and Netflix stream smoothly and look great. 720p video from mp4 plays flawlessly and looks absolutely gorgeous. However, it will not play 1080p files -- they lose sound and lag badly (tested with stock player, MoboPlayer, and RockPlayer Lite). 720 or less and you get vibrant colors, sharp resolution. This is pretty well an amazing screen by my standards. I know there are higher spec screens out there and some play 1080, but I can't imagine why I would need video to look any better than this on a 4" screen. (Note: there is *not* an hdmi out on this device, which would be the primary use for 1080 capability.) MoboPlayer's brightness slider is especially welcome as you can tweak the video brightness on the fly and get optimal performance from the screen.
Camera is decently responsive. It takes about 2 seconds to load from the icon off the menu, and each snap is just under 2 seconds from pressing the button to ready for the next pic. If/when this gets the ICS update that should speed up.
Wifi locks on quickly and works great. WPA2 no problem, fast, easy.
Stock browser is quick, pages look great, render well, zoom, scroll, etc., are pretty swift and without trouble. Very little checkerboarding when loading most pages, essentially none once most pages load. However, highly graphics-intensive web pages take a second or two to fully load and have some checkerboarding when scrolling them and some lag as well. This is pretty minimal except if you have auto-fit turned on. With autofit on, it can get pretty bad on a more demanding page. Testing this with The Secret World | Funcom really accentuated the issues. That said, I don't forsee this being an issue for 99% of the browsing that 99% of the users do, and even when it is being rough and laggy, it is still usable.
Opera works much better. So far this is my preferred browser for this device. Dolphin Browser HD and Skyfire are a little laggy and are not rendering all pages as completely or as well as Opera or stock.
GPS lock is accurate and reasonably quick. Faster than my old Droid 1 and spot-on for navigation, etc.
The battery is holding up pretty well, but this is definitely no BlackBerry. I am getting a day of standard use out of this between charges, especially after the first couple rounds of conditioning. Hotspot and GPS chew through battery, but even with 4g, I can do a pretty solid day's use before the 15% warning. Screen brightness controls will help in this regard, to be sure. I have no controlled tests to report, but I can say I unplugged it from the charger at 8am this morning, have been installing and uninstalling apps, playing videos, dowloading files (about 500MB worth today so far) and doing web browsing. I've also rebooted it three times to ensure the tests are off a clean boot without any residual programs running in the background. The system info says 7h 19m on battery and it is currently at 30%. 57% of the usage is screen.
The physical keyboard took two days to get used to, coming from Droid1. It's nicely spaced, good tactile response to the keys, and other than getting accustomed to the fn key placement being different with 5 rows than 4, it's all smooth sailing. The biggest thing that takes some time getting used to is the placement of the shift key and the menu keys. The home key is where you might expect shift and that can be an irritating error. On day 3 of usage and I am finding the keyboard quite good. Give me another week and it will be great. I should mention here that for me the absolute best reason to have a physical keyboard is that I can scroll through the original text of an email while I am writing a response. The nice spread of the keyboard and the 4" screen make this a wonderful device for my uses.
Build quality is good, feels reasonably solid, but I would say the Droid1 feels like a more solid and durable device. If I drop this, I fear it may not hold up as well.
There is no doubt we could really use a custom rom for this device and root, if for no other reason than to get rid of the silly amount of bloatware installed. The useless golfing game and racing game demo pre-installed hog massive amounts of memory (240mb) and the system will not let you uninstall them (it acts like it will but they will still be there no matter what you do). Hopefully we will see CM come in for this in the near future.