Even when you look really close, the new Mac mini looks like a clone of the previous version. It's also more of an update than a complete overhaul, and that means it's still a very nice mini PC.
It's a compact mini PC, that you can use as server (combined with MacOS X Server if you want), HTPC or just as computer. It has a very high-end finish compared to other mini PCs, with a solid aluminium chassis and a good array of connectors in the back. It looks nice that way, but isn't always the most practical solution. If you want to plug in a USB stick you have to do so in the back.
The new Mac Mini runs on an Ivy Bridge processor, unlike the previous iteration that had a Sandy Bridge chip, so it should definitely be faster. And unlike the previous Mac Mini that had a version with dedicated graphics in the shape of the AMD Radeon HD6630M, the new Mac Mini does not come with a separate GPU. The integrated graphics of the Intel processor were apparently fast enough for Apple.