I'm running Reaper on a late 2011 MBP 17in, almost exclusively vst (but you have to use the mac ones) and it's very stable.
It only crashes when I forget to plug my ilok if the session needs one, it freezes there, I think it's because the waves authorisation window when the vsts are loaded appear behind the reaper window so I can't access it and need to force quit reaper, plug it, and start again... No big deal since reaper is a pretty clean installation anyway.
Otherwise, absolutely flawless in my experience with only vsts, and using legit quite well known plug ins from big companies, plus occasional freebies that are mac compatible.
If you switch you basically have to think again about your vst options, from scratch, if you were using a lot of vst freebies from here and there.