Pixelmator is quite nice--especially for the price. And I've been using it for a while for my own personal side projects. 2.0 came out and added some nice features.
Alas, it has issues. The big ones:
- it's buggy. I think it's a bit premature to call it '2.0' IMHO. Still feels a little beta.
- doesn't support full range of PSD layer information. It can open PSD files, but since it can't bring over all the layer effects and styles, it's really not practical.
- very limited export abilities. The big one is PNG files. If you let it compress them, you get big color shifts. If you export it as a non-web PNG, it's huge, and then you have to use 3rd party tools to further compress.
I think it has a lot of potential, and eventually will be a great runner-up, but it still won't be PhotoShop.
As for slicing, it does do that (aside from the PNG issues). (I'd suggest not using a 'slice n dice' workflow anymore, but that's a different discussion...)