>1. How reliable are they?
I have many Soviet RF's and have been using them for just over a year now, I have yet to have one break down thru use. On the other hand I have had several arrive not fully functional i.e. pin holes in the shutter curtain, shutter not operating correctly due to grease/lube going thick, dirty viewfinder, RF out of alignment etc. Most of the problem cameras have been because of me looking for a bargains (you get what you pay for, yeah I know) or buying older rarer models (less to choice from) or taking pot luck with a new seller. Btw: All my cameras have come out of Russia from ebay auctions. IMO its better get one that listed as "like new" or "excellent" by one of the better sellers than to try and save $10 and get a bargain camera that may not be the best as a user.
>2. Which model is the best user?
IMO,
(With speeds down to 1 sec) - FED3, Zorki 3M
(with speeds down to 1/30) - FED2, Zorki 6
FED3(b) is the best bang for your $$ IMO
>3. What lenses wide-tele are best?
This is just from my experience and what I've picked up form web posts.
Best wide is the Jupiter 12, there are Soviet 28mm & 20mm's as well but for the prices they go for (if you can find one) you would be better off getting a CV lens for a user. I've got a chrome J12 that I really like, nice images.
For standard lenses most of the 50's are good I've found unless they have "cleaning marks" (more like rubbed for years with steel wool

) ... IMO pick of the bunch are Jupiter 8 (f2) & Ind 61 L/D (f2.8). I've also had very good results with the Ind 26m, Ind 22, Ind 50. The only real hit and miss 50mm is the fast Jupiter 3 (f1.5), some are great and some are rubbish.
For Tele's you have the Jupiter 9 (85mm/f2), its a great lens but lots of them have focus problems from being stripped and put back together wrong and are very hard to put right. There is also a 135mm but I don’t have one and haven’t heard much from users on it.
As far as ebay sellers go I've found the soviet sellers to be good people to deal with in general. While I don't like to recommend sellers "alex-photo" and "cupog" come to mind as good people to deal with.
Good Luck