The most striking change to anyone who's opened a previous-generation mini is the screw-off bottom. With a simple counter-clockwise twist, you've got access to the RAM bay and fan. No more putty knife. Well done, Apple!
Apple's designers got creative with this machine in a number of ways. The unibody construction required the two antennas to be carefully placed next to the logic board. Also, the fan has a very high number of blades so it can push a maximum amount of air. The fan's screws are isolated with rubber dampers to keep noise to a minimum.
Getting at the hard drive (iFixit's unit only had one) is an ordeal. Expect to remove just about every other part before gaining access. And I thought the white iBook was a pain to take apart.
Meanwhile, the folks at Macminicolo have taken apart a dual-drive mini meant to be used as a server. That second drive is much easier to get at than that in the single-drive model. They also provided some nice side-by-side shots with a white plastic mini; the aluminum model is so much better looking it's not funny. The whole thing is three pounds, and macminicoloco says, "It feels less like a brick...and more like a laptop without a screen."
Finally, Macworld kept their unit in one piece and did a point-by-point comparison to the Apple TV. Could the mini be the next-generation Apple TV in disguise? By comparing features like connections, physical media, content and price (a biggie, as the new mini is seven hundred bucks), Chris Breen fills in the details while letting the readers make final judgement. As for me, I'd love to swap my Apple TV for a sleek new mini.