I've owned both the MiG 50 and the MiG 50H (Tube Midget). The MiG 50 sounds pretty good clean but must be cranked up to ear-bleeding volumes to get it to give up the goods. It doesn't sound exactly like the JTM45/Bassman/etc., though.
The pots and switches are pretty cheesy. The pots are also PCB-mount IIRC. If I were to get one of those, the first thing I'd do is swap them out. The overall parts quality is fairly good. Most are Soviet military surplus.
The other problem is that there are fairly high voltages in that amp, so it is bright and clean. It came stock with Sovtek 5881 power tubes, which are bland, neutral sounding tubes. The Sovtek 5881 sounds good in hifi amps, but isn't optimal for guitar amp use. It also isn't a real 5881, it is a Russian military tube that was used in MiG fighter planes. It is not in the 6L6/5881 family of tubes, but it is close enough to use in 6L6 applications.
The good news is that the transformers are pretty good. They are pretty hefty, so they are unlikely to blow under heavy use. The one thing I don't know about is the OT. If it is set up to run the Sovtek 5881, it most likely won't sound good with real 6L6/5881 types of tubes. I never subbed in different tube types in my MiG 50 when I had it so I don't know if it sounds good with 6L6 types or not.
tung