Don't buy the kit unless you are *very* handy as a do-it-yourselfer and have a good set of tools and a workbench. If you don't have a Dremel, you'll need one.
It's not an easy "bolt-on" operation, despite what the sales literature says. You completely dismantle the entire AK and end up replacing almost all parts. The kit doesn't necessarily fit together well, mainly because all AKs are different (being sloppy fit in the first place). You use the Dremel to machine all the parts to get them to work together. Work slow. You'll learn a lot of new swear words by the time you're done.
The trigger wire is a thin, brittle piece that doesn't work in all AKs. I broke mine, then created another out of beefier wire from landscape rods. Getting the trigger reset to work was a major pain. I ended up getting the trigger mechanism to work by using a combination of old and new parts, plus a lot of "tweaking" on the parts with the Dremel.
The previous poster was right -- the trigger has a very spongy feel. By polishing the moving parts and playing with the mess, I got my trigger feeling pretty good. I have two friends who built kits also, and my trigger is the best of the group. I also agree that taking off the front sight and putting on an optic is a good idea. The extra high front sight looks goofy. I put a Trijicon Reflex on mine.
I also had a nagging problem of the trigger binding and not resetting. This only happened at the range. I narrowed it down to heat-related. When the barrel got warm, it would bind with the trigger (which is just below the barrel on the bullpup). Some Dremel work on the trigger to give it more clearance solved the problem.
Still ready to do it? After all the bugs are worked out, it's a fun weapon. The legendary AK reliability is still intact. It's very compact, although it seems to kick a bit harder than before, probably from being so small. I put a Giles tactical sling (sized for an Aug) on it and it works fine. I also got some 20-round AK mags which seem to fit the gun better (for light weight and compactness).
Oh yeah, forget about the gun if you're a lefty.
I've got over $1000 invested in mine. If I had to do it all over again, I'd have bought something else. If you don't want to build it, my advice is to try and buy one that someone has already built and worked the bugs out of. Want to buy mine?