As a Mac user, I would like to apologise for MTW. We are not all like that.....
Personally, while it's a little disappointing the Mac version of Multiwinia is not ready yet, and that we don't know when it will be, I would like to say a huge thank-you to Introversion and Ambrosia for producing Mac versions AT ALL!! Many, many developers do not even bother - so to find a developer with such unique and fantastic games, especially such a SMALL developer, who takes the time to develop, test, and release Mac version of those games - well, all I can say is, again, THANK YOU!!
As for the whole Mac vs PC thing - well, it's a little silly. I used to be rabid anti-Microsoft, but you know what - they're not really that bad. (Well, except Vista....

Both platforms have their ups and downs. I generally prefer using a Mac over a PC for general productivity stuff - I find the Mac a little more fun, and a little less stressful to use in general, but to be honest these days, there's not too much difference any more. I have quirky mac stuff happen every day, just like quirky windows stuff happens.
For games - well, sorry fellow Mac users, but Windows has more choice by far. Mac is certainly improving in this respect - but slowly, oh so slowly. Games just are not, and never have been a priority for Apple. Whether this could change given the success of games on the iPhone App store remains to be seen, but I'm skeptical.
I'd suggest any Mac user who cares about gaming to take a step back, and support our Windows friends where gaming is concerned. With all the doomsayers about the "death of PC Gaming" recently (which, admittedly, is far, far over-exaggerated) we all need to stick together in my opinion, and show our support to keep the PC (and, where possible, the Mac) a strong, healthy platform capable of nurturing such innovative and talented developers as Intorversion and Ambrosia.
Hmm I think I rambled on too much - anyway, just my 2c (or tuppence, or whatever)...