The Galaxy S2 Wikipedia page is quite packed with information!
http://en.wikipedia.org/wiki/Samsung_Galaxy_S_II

Some things that I thought was interesting.

The MHL connector on the bottom of the phone (think: uncompressed HDMI via USB) can supply power from an MHL enabled device! This means that if your S2 is playing 1080p content on your TV, you don't need to worry if the device is charged for the entire playback.. Very nifty.

The S2 also supports USB On The Go (Host)! This is very interesting for those hardware tinkerers out there, to pull info from a USB storage device, or drive a printer.

Also revealed are some accessories including, a dock connector (boring, but useful), a special capacitive stylus (now we're talking), and an offical case/battery extender! Interestingly, the case/battery seems to bring the devices thickness in line with other smartphones.
http://www.journaldugeek.com/2011/03...ung-galaxy-s2/

If I were to buy a smartphone, this would be at the top of my list.