IOS7 is compatible with all apple mobile devices, though I highly suggest not downloading it on a 3S or below
It's really funny how at before 12:00 at school, the wifi was fine. After 12:00 the Internet lagged up so much because everyone was downloading iOS7
I got it on my mother's iphone and it isn't as good as apple portrayed it. I am going to uninstall It
I think it's like 800MB or whatver for iPhones and such, my iPad 3 and iPad mini downloaded 2,9GB ;P Apple is awesome..
But you also lose warranty, and although your warranty with Apple may not seem too good, it can be useful, as I found out the other day
I personally haven't jailbroken my phone because I use it mainly for business calls, texting, and maps