I've handled/shot three different types of AK bullpups.
Valmet M82, Norinco Type 86S and the K-Var AKU-94.
The Valmet M82 was the best overall. Better fit/finish, quality, accuracy, trigger pull and reliability. The Valmet M82 is no longer imported, but they show up on the auction sites every now and then in the $1500-3000 range.
The Norinco Type 86S was the second best. Good quality, fit/finish was alright, accuracy was similar to traditional AKs, trigger pull was managable and reliability was good. The Norinco Type 86S is no longer imported, but they show up on the auctions sites every now and then in the $1200-3000 range. The top charging handle would often pinch/draw blood when used, highly recommend the use of gloves.
The K-Var AKU-94 is acutally a bullpup kit used to modify AKs into a bullpup configuration. Regardless of the base AK, the AKU94 kit did not have very good fit/finish and the trigger pull was horrendous. K-Var sold the AKU94 bullpup kit during the 1990s, however due to bad reviews and slow sales they discontinued it. During the mid-2000s, K-Var sold the AKU94 design to Century International Arms. Century now uses the AKU94 bullpup kit on their Romanian AK kit guns. The Century International Arms 1975 GP AK bullpups still retains the crappy trigger pull of the original K-Var AKU94.
If you are interested in an AK bullpup, I recommend either the (5.56x45mm) Valmet M82 or the (7.62x39mm) Norinco Type 86S.
I do not recommend the original K-Var AKU94 or new Century International Arms 1975 GP AK bullpup.
"If someone has a gun and is trying to kill you, it would be reasonable to shoot back with your own gun.” - Dalai Lama (Seattle Times, 05-15-2001).