We use storable extensively on many different systems with very little trouble.

Version problems are potentially still there, but only if a newer version stores a data type that an older version cannot handle. (it now will try to handle the data from the newer storable instead of just croaking)

I second your comment about nstore though. I'd highly recommend using nstore by default. Having to convert a couple million stored objects because you add a 64bit machine to your farm of 32bit machines sucks.