I've had a couple modified Kiev 88CMs over the years. Both were by Hartblei and both were pretty good. I wrote a small article about Kiev cameras on my site, you can read it here: http://www.jimadsonphotography.com/info/kiev_info.html
My current opinion has changed a little though. Although I still think Kievs are decent cameras, I think their position as the best way to get into MF on the cheap is in serious danger. As many people have mentioned already, there is an abundance of used gear on the market that is of dramatically higher quality than the Kiev. Since getting rid of my Kievs, I have had a Mamiya 645 Super and (currently) a Hasselblad 2000FC. I paid less for the Hassey and Mamiya than I did for the Kiev. The difference in fit, finish, and reliability is beyond compare.
Several people have mentioned that lens prices are not falling as quickly. This is partially true, but depends on exactly which lenses you are talking about. The Mamiya 645 lens prices are falling like rocks, and often you can find them used for the same price as a new Kiev lens of similar focal length. Now you may think it's invalid to compare used to new, but I disagree. The fit, finish, and quality control at the Kiev plant is so bad that new Kiev lenses are often in worse shape than decent (even pretty old) used lenses from better manufacturers. That doesn't even take into account optical performance, which can be hit and miss with the Ukranian made lenses. A few years ago, they were dramatically cheaper than the better brands and that made it worthwhile, but that's not so much the case anymore.
It gets even closer if you compare the best Kiev lenses- the Carl Zeiss Jena lenses for Pentacon Six cameras- to the other manufacturers. CZJ lenses have not been manufactured since the late '80s, and thusly are available only used. They are much better in build quality and (usually) optical performance than the Kiev lenses, so they are a better comparison to the lenses offered by mainstream companies. The problem is that while Mamiya, Zeiss, and Pentax used lens prices have been dropping like rocks, the Zeiss Jena Pentacon lens values have been steadily creeping up. Most of them are actually more expensive than the Pentax and Mamiya lenses, and are about the same as older Hasselblad Zeiss lenses.
Overall I think that Kiev's advantages have all but dried up.