I have a pretty old HTPC, but it has no problem playing back full HD material, so I've not felt the need to upgrade. Lately however, it's been struggling for a bit, even with the standard skins. But with Apollo, everything's very smooth.
It's also a very stylish skin, without going overboard with flashy animations or other unnecessary stuff. As I'm writing this review, I'm using version 188.8.131.52. I'm sure the upcoming versions will be even better.