I want a Mac mini for light use and the occasional minecraft server. I was wondering if I should go with the current ivy bridge model, or wait for the haswell refresh? Iris pro would be pretty nice to have. And ac WiFi would also be nice. But what do you guys think?
Ivy Bridge will do just fine. While IrisPro is nice, it will also pretty pointless if you don't plan on making use of it, and it sounds like you wont. As a general rule, I recommend against any Apple hardware due to absurd profit margins/poor value, generally not being the best (especially in given price range), and the company's politics within the industry (they're stupid patent trolls).
Getting an Intel NUC w/ Linux will be a much better price/performance (weaker CPU, similar graphics, doubled the RAM, in at just over $400), and can run up to 25 players as a dedicated server well, assuming you have the upload speed.
http://secure.newegg.com/WishList/PublicWishDetail.aspx?WishListNumber=24592246
Just playing with the idea of something more on par (price-wise) with the Mac Mini is the Intel NUC with a Haswell Core i5, although currently out of stock. This little "build" has 4x the RAM, 2.5 times the GPU horse power, and storage about 5 times faster (granted at half the capacity, but expandable) for the same price. There is no comparison here...
http://secure.newegg.com/WishList/PublicWishDetail.aspx?WishListNumber=31912448