mate!!
Fantastic car, mine's a daily driver and she hasn't put a foot wrong. There are a couple of pretty minor issues (as with any new model) but they are all sortable under warranty. If you're buying outside of warranty I can't imagine you'd have too many troubles as long as you do all the usual checks.
Have had a standard zed on the track (Anglesey) and it was far better than I imagined, really involving and nice and balanced on the limit.
The Boxster S is a faster car but theres little in it and I doubt you'd notice the difference with every day driving. Personnally I far prefer the sound of the zed to the porker though. Plus the zed is a fair bit rarer on the roads.
The general consensus (I think) is that the interior of the MY06 is a better quality than the earlier model but I have a 54 plate and its a nice place to be every day, certainly more special than anything you've been used to in, say the Type R
The long and the short of it is that if you buy the right car then you won't fail to have a big etched on your face!