I can comment on aspects of your questions. I've been to Saffire twice (stayed in basic room and in pavilion) but not SOL.
Access: Flying to Hobart vs Launceston - about the same drive time as I understand it; an easy drive from Hobart (less than 3 hours as another poster has said). Saffire operates a lounge at Hobart as well - pleasant on departure. Hobart is enjoying a real renaissance right now - you could consider an extra night or two there to sample some restaurants and/or MONA (personally I think Hobart has more to offer than Adelaide these days but YMMV).
Rooms: the plunge pool in the pavilion is nothing special. It is on the front side of the pavilion (so no views). It is not large. We didn't consider using it. Personally I think location of the room is more important than room category at Saffire - you want a room (any category) that is along the path to the "right", towards the pavilions, as these rooms are a bit further from the main building and feel less overlooked (not that overlooking is much of an issue). They are also slightly more elevated than some of the other rooms. The pavilion is divided into three primary living spaces - separate bedroom, dining area (which we never used) and sitting area. I actually preferred the more open feel of the entry level room. The mid-category room is worth considering too - these have an attractive soaking tub with view.
HTH