Here's a gotcha on MIDI interfaces I ran into.  I have a Peavey AT200 guitar that get's updates and can be controlled via MIDI.  Antares provides a cool little application to create and store presets in the guitar that be be recalled later without being connected.  It's a slick setup.
 
The problem is that out of all the MIDI interfaces I have, the MIDISport is the only one that can handle large sysex messages.  According to Antares, MIDI interfaces that rely on Windows class drivers won't work.
 
If you don't need this kind of thing, then no problem.  However, you have MIDI gear and will be sending large sysex messages, check out the details before you buy an interface.
 
 

I was fast arriving at the same conclusion when everything came together acceptably after all. I've got my Roland piano next to the computer desk with my old Yamaha MU10 daisy-chained through that via USB and everything works! I think this suffice for now as I can use it. It seemed harder to source sound components than when I built my last system and the Fatali1ty with a front panel I could plug a guitar straight into was easy to get. Sound cards I've been reading about lately seem to be more about whether you can hear someone behind you in BF3 (whatever that is. :) ) 

That guitar sounds interesting. It's a long time since I played pubs but something like that would have been amazing. I remember Casio doing a MIDI guitar but how good it was I don't know. I shall now Google 'MIDIsport'. :) 

The AT200 isn't a MIDI guitar.  It just uses MIDI for software updates and as a control option.  They are cool though.
 
I only mentioned it because of the limited number of MIDI interfaces available with drivers that work properly.

I just watched a demo of the AT200. I've never seen anything like it. Amazing. My guitars were in tune when I bought them.

DuckRumble
I just watched a demo of the AT200. I've never seen anything like it. Amazing. My guitars were in tune when I bought them.

  It does much more than just tune.  It's a cool concept that works pretty well.