Oh and front ends aside ---
1. First you need to figure out the types of games you want to play, as others have said.
2. This will help determine how good of a computer you will need.
3. It will also help you determine what controls you need. Could be just joysticks and buttons. Or else you might want things like a trackball, spinner, flight stick, driving wheel, guns, etc.
4. The as far as bells and whistles go... I'm trying to think of what might be new since 2007. But some extras are:
- keyboard encoders, instead of hacking keyboards manually.
- lighting controls LEDWiz, PACLED -- and the lit up controls to go with them
- There are now MANY options for joysticks and buttons, but of note the "best" joystick is the U360. So if you have the cash, you could think about those.
So the skys the limit as far as what you want to spend. There's just so many options out there for everything now. So figure out your budget and go from there.