I have no idea how good or bad Medvedev is, but it is unlikely he is as scary as Putin.
And Putin is really scary.
He's brilliant, ruthless, experienced, and has presided over a skyrocketing russian economy for years. His mistakes are buried. He'd proudly kill his enemies by hand for the world to see.
It is amazing how mismatched we were (Bush/Putin) in the last 8 years.
If Russia goes through some internal pain and confusion, and the spillover is isolated, and the end result is Putin isn't there, that has to be a good thing for most of us.
If it happens during low oil prices (now!), it'll have minimal effect on us economically.
We are fucked anyway, what's a little more instability for a while.
Unless they flip out and start tossing nukes our way.
That could be a bad thing.