If you're looking for a MIDI Controller guitar you should definitely consider the "You Rock Guitar." I love mine and at about $200 it seems like a really good deal considering all that it is capable of.
It may look look like a video game controller (and it can actually be used as one) but it really works quite well. If you've got some sweet VSTi synthesizers (and/or samplers - even drum machines!) then you can plug this thing up via USB and control them. I use mine with REAPER but I believe it works well with any software that has MIDI input.
I've been very impressed with how responsive it is so far. I wasn't really expecting it to work as well as it does. Nice surprise. Yes I have had some dropped notes with finger style playing but I think that may just be a matter of adjusting the settings and how I play it (you have to be a bit more precise with a MIDI guitar than you do with a real guitar.)
On the other hand, this guitar is much easier to fret than a real guitar as there are no strings to hold down (the only strings are for the picking hand.)
It's got all kinds of on board features and sounds but to be honest most of them seem really cheesy to me, I say skip all of that silliness and use it as a MIDI controller that's where it's true awesomeness lies.
I plan on sharing some samples of the kind of things you can do with the You Rock Guitar as a MIDI controller in the future, in fact I may just edit them into this post (after I put them up on YouTube.)