I think what it comes down to is, yes, you should buy a Galaxy S2. It's the best you can get for your money(assuming you don't want to spend $700), and it is relatively future-proof.
Phone: AT&T Galaxy S4 (SGH-I337)
Firmware: Stock Rooted (waiting for bootloader unlock)
Launcher: Nova Prime
Previous phones: Samsung E317, Motorola KRZR K1, Sony Ericsson w580i, Samsung Sync (SGH-A707), Sony Ericsson F305, Blackberry Bold 9700, Blackberry Torch 9800, AT&T Galaxy SII (SGH-I777)
So say we all.