I gave my i7 hackintosh to my wife when her computer died. I was ready to roll up another when I learned about the 4,1 to 5,1 upgrade hack with the 2009 mac pro. So, I've spent the week sourcing parts and it's done.
Ended up finding a mint 2009 mac pro which i upgraded to a 3.3 W3680 xeon, 500gb SSD (OSX), 256gb SSD (windows 8), 24gb of ram, and a GTX680 mac edition. At the end of the day everything cost me around $2500. Yes, I could have put together a monster gaming rig/hackintosh for that money, but I'm glad I went this route.
Games I play in OSX are GW2, Starcraft, Eve Online, Borderlands 2, League of Legends (great mac port btw), and a few others. With the exception of GW2, I can play all of these maxed at 2560x1440 in OSX. GW2 under OSX gets 50-60 at medium settings, under windows it gets 50-60 with everything maxed. Under windows I play World of Tanks, Planetside 2, and MW online right now.
This gives me the best of both worlds for "my" needs. The mac pro has plenty of easy to access storage. I keep my important documents, music, video collection, and other data on a 2TB drive and I have a 3TB drive for TM that backs it up along with the boot drive. I could have done an iMac, but i would have had drives hanging off of it, plus IMO the 680MX is just on the edge of adequate for games at that resolution, plus i already had a really nice 27" led lcd.
I doubt I'll be a customer of the new mac pro as it seems to be designed for "pros" using highly threaded apps for video and music versus the power enthusiast, which is a pity. Also I don't think it will be that great for games either due to the video cards being tuned for video/2d and the cpus will have lots of cores, but lower clock rates compared to consumer offerings (much like it is today).
just my .02