I've owned a fair few smart phones, the iPhone, htc touch hd, hd2 and now the dell streak.
1. the size
this was the biggest concern for me as i had a feeling holding it up to my head would make me look stupid. if it was a standard phone i'd say it was too big but! with everything the phone does the size is perfect. the screen is large enough to read books play games (i've even got a gameboy and snes emulator on it) up against my head it's large but i don't mind that; if it really bothers you it comes with a headpiece and mic that you can just plug in (or get a bluetooth headset)
size 5 stars all my worries were taken care of after a few days use
2.) Battery life
battery life is great better than any of the smart phones i've used before. my windows mobile htc touch hd would last a few hours with just regular use of the internet and calls. my android has lasted 4 days on one charge with regular use of the internet and even reading a book for a good hour.
3. sound quality
this is my only gripe with the phone, the sound quality of the external speaker isn't great it's a bit muffled. the call quality i get on the phone is good maybe a tad crackly but i think that may be my poor reception.
there are tons of apps and games, obviously not as many as the iPhone but there are a lot of high quality ones and the app market is getting larger and larger every day. easily competes with the iPhone market for quality apps
4 stars (5 if it had as many as iPhone) but like i said I'm very happy with it
the screen is super tough i accidentally dropped my mug on the screen almost had a heart attack but there wasn't even a scratch and i dropped it pretty hard. not sure i could say the same for my old iPhone. i don't even use a cover on the streak it's that durable.
the speed over the internet is very fast and the speed of the phone in general is very fast (there can sometimes be a very slight lag in dragging the home screens) not enough to be an annoyance though
the keyboard isn't the best i must say. maybe i'm just not used to it yet but i make a lot of mistakes on it and find myself having to go back and retype something. i'd give it a 3.5 out of 5
i think i need to get used to it though. (hitting some of the middle keys can be a problem for smaller hands because of the landscape size)
The android os
i've used the latest os and I've used this os they're very similar with Dells additions to it. the new os release in the near future will be great im sure knowing what they've done with 1.6
camera quality is good not amazing in the dark but then again i've never found a great dark shooting camera phone
i wish the camera was 8mp but wishes are wishes. the 5mp is good enough
all in all this is a great phone.
i thin if you're looking at any smart phone look at this. if you want an iphone...seriously consider this.