i recently moved to a new mac pro from a last gen imac for my sB setup.. the stability of the app has increased 1000%.
i find that kinda weird. but, makes me happy nonetheless.
i've never used the multitrack option ( i assume you need them for stems and the like?) but i have a work flow now that is fast. i dont do fancy things with plugs, just run audio thru analog loop and capture, trim the heads and tails, put in marks and burn. once in a blue moon i need some fancy xfading that the amazing fade editor in sB allows me to do.
i think the only way for you to know is just to run a parallel system for a minute that u can use during unattended/not-time-critical sessions to get a feel for the stability and usability.
the upside for me is that i am so fast with OSX and my related utilities that run on OSX, any slowness in sB is well worth the speed i gain other places.
sB tho, still has TONS of gotcha's that will drive anyone crazy.
audiofile engineering is working on an update (a while off i assume tho) to add mature "mastering" features to Wave Editor (such as analog loop, etc etc etc)
i've given them my wish list and EVERYTHING i asked for was on their list too.. which makes me hopeful