Its Worth it!!!
I had a GK-kit installed on a G&L commanche (strat). It has opened up a whole new world to my playing. This is especially true for studio work. I make keyboard players nervous (lol)!!! He hasn't been late to practice, or missed one, once since I got it!!! I even got a few extra studio calls due to its unique sound. I got it installed by Jason over at "Too many Guitars" (Tucker, GA). Unless you are a good to great guitar repair person or luthier...don't try to install it yourself!!
I use it with a Roland G.I. -20 midi / usb interface. My synth modules of choice are Emu Mo Phatt, Triton, and a fantom. The ability to toggle switch between pure guitar, guitar synth mix, & pure synth is great.
I have had this set up for a year now. I can honestly say its worth the money to ensure your midi rig is road worthy. The GI-20 only comes with a short (expensive) 13 cord and there are no rack ears included!! Of couse there are certain patches that have to be programmed for sensitivty, bends, and other traits specific to those patches. You can't just freely strum certain tracks. However...so far it has held up. Nothing is loose and it still works. Its like having a hemi engine in a honda accord!! The shocked & puzzled looks are worth the money alone. Since it is totally internal you can't tell unless your up close or know what to look for.
When used with keyboard modules it really sounds like a regular keyboard playing. Its not a knock off. Its not a magic solution right out of the box...but it dang close. With practice, patience, and programming this is a heck of a tool for the money. The only comparison is a parker or godin which is crazy money. This is much better than the ready made midi guitars on the lower end of the guitar spectrum. SO take your favorite, high quality axe and get er done!!!