Point 2, steam is MUCH easier to install on multiple systems, you try installing your MAS store copy on a PC
Well, excluding PCs from the equation of course....
Though one advantage of MAS installs on multiple machines is that you can actually play each copy simultaneously, unlike Steam. That's pretty convenient for family sharing.
Point 3, Fair play, if its cheaper, and by Cheaper i mean half the price or better then the saving outweighs the benefits of buying on steam
And I even get iTunes content for even cheaper by getting iTunes gift cards for 20% off at Best Buy (or Walmart), then using both my rewards credit card and my Reward Zone membership together, and then on top of that, I then use my Bank of America's Add it Up Rewards program when buying on iTunes. All together, I always get up to 30% on all iTunes/App Store/iBook store/Mac App store stuff
Point 4, i think the only thing stopping the Mac and PC versions of Boarderlands 2 from playing nice is that they both have to have the same DLC installed, and the DLC for the MAC is lagging a few months behind the PC version, so you can cross platform play as long as your PC buddies don't upgrade to the latest and greatest versions until you get your Mac upgrades.
From what I read from Aspyr's updates, the Mac (Steam) version and the PC version were only out of sync for a couple of days this week?
Point 5, id love to ditch windows, but my 2TB Steam library kind of needs me to run windows, that and my love of not waiting months for games that's out now to be ported to the Mac and sold to me at +10%or more the cost the PC version is selling.
I am already well on that path to an OS X centric existence myself, and would love to be 100% OS X. But sadly of course, I doubt I'll ever have a chance to ditch my Windows partition entirely for the very same reason you stated. However, I've conditioned myself to be patient to wait for titles to be ported to Mac. Both Feral and Aspyr are doing an excellent job of porting titles faster than ever before. Borderlands 2, Lego Lord of the Rings, and Bioshock 3 have all been released (will be, in case of BioShock) within 3 months of their Windows counterpart. And Blizzard remains as the top big budget Mac developer with day 1 Mac releases. In reality though, whether one buys on Steam, MAS Game Agent, etc., this truly is the best time to be a gamer on the Mac.
As for the 10% higher mark up. Again, for me, all my purchases are actually comparable to Steam prices, if not lower when I stack up my deals. So I'm pretty content
