$650 is a good price.
If you've got a need for it, buy it.
I gave $699 for mine a few months ago...plus the transfer.
Problems I had with mine:
The front sight was obviously canted to one side. Ruger fixed that on their dime...and...fitted a spare firing pin while they had it for no charge.
The bedding on mine was incredably sloppy. I fixed that myself.
The gas block was catty-whompus, even after the return trip to Ruger. I fixed that myself too.
The rear sight base wouldn't stay put and I didn't care for it's mickey-mouse adjustment system. I solved both problems by installing an after market "Tech Sight".....which added an additional $60 to what I've got in the gun. That was done, and the trigger issues addressed, as soon as I got it back from Ruger.
Getting to the bottom line:
IMNSHO, Ruger has still not offered an "out of the box" Mini which is what I would call a "serious rifle". The newer ones are a lot closer than the older ones, but still no cigar. Some of the problems with mine were due to a lack of craftsmanship but some are design issues, pure and simple. Either way though, I would think that by now, Ruger could do better.
On the other hand, in spite of the extra work, time, and money it took to get it shaped-up, I like mine a lot. And it'll shoot. In fact, regardless of what you might hear from the "just buy an AR cowd", it will now outshoot my Son's Bushmaster when both are using the same lot of M193 Lake City ammo.
Hope this helped with your decision.
DGW