I used Roads of Russia quite a bit, although only in European Russia. It is generally pretty good, except when it isn't...

As Walter says, a fair number of roads are off by several hundred meters, but also some major highways do not seem to be in the right place. But once you learn its tricks, this is not that big of a deal. It is more irritating when it tells you to go somewhere, and then all of a sudden it changes its mind and tells you to go in some other direction. Not exactly confidence inspiring. Let's just say I never leave home without a paper map.

That said, for all these complaints, it is really great to have (at least in European Russia); just today I returned from a trip to Belgorod, and used RoR to navigate back via all sorts of tiny backroads, very cool. Sure, I could have done it with paper maps alone, but it would be kind of a PITA and signage is not great on most of these little roads.

The biggest problem of all is the requirement for the distributor to reflash your Garmin device, I can't see this as being practical for anyone outside of Russia. You can load RoR without the reflash, but you can't read any city names, which makes it of rather limited utility.

Finally, for anyone coming to Russia, I highly recommend staying off the main highways as much as possible. They are choked with trucks and speedtraps, and just not very pleasant. Staying on the backroads is much more fun, but if you can't load RoR you'll need a decent atlas, the ability to read Cyrillic, and lots of time for when you get lost (and you will get lost...).