Honestly, if there's not a significant change to the iMac this year (and we're probably looking at October here), I might go for a Windows desktop. I think the iPhone is the best phone, the iPad the best tablet, and (arguably) the MacBook the best laptop (it certainly has been in the past and it's the only laptop I'd consider, even with the flaws). But I wouldn't say the iMac is the best desktop.

I think it's very good, but I'd love to see some changes, like adjustable height, smaller bezels, more upgradeability, less reflective display, backlit keyboard option, better mouse, return of optical audio...I know some of that's just a pipe dream.