I bought a Kiev 6C and a 250mm lens from Arax. All good. But in todays market you can get Pentax or Mamiya 645, Bronica 6x6,Mamiya 6x7 all for similar amounts of money. They all have features that are worth something. With the 645s you can stick the Kiev lenses on the front with a relatively cheap adapter.
The main advantage of the Kievs is the multitude of lenses. Price a fisheye for any other MF system. I'm going to agree with some of the comments that MF lenses have dropped in prices but they still aren't in Kiev price areas. Nor are they common like the Kievs.
On reliability my broken MF is my Pentax. My Kievs are just fine.
I don't know. I personally would be hard pressed to reccomend investing in a Kiev system right now unless you're a lens addict. It's great that I own a 45mm,65mm,80mm,90mm,150mm and a 250mm. Not to mention I intend to add a 30mm. But do I really need all those?
BTW I find using the waist level finder with all that implies the best way to use the Kiev 60 or 6C.