I own and love pixelmator, especially given the price, but I think it bears mentioning that it doesn't have full PSD support. While understandable, not being able to edit a type layer within a PSD (type is rasterized upon import) can be problematic when working with others or updating a file.
And it's not just cheaper, it's less buggy and faster.
Adobe CS isn't just unpopular because of its pricing, it's really inconsistent, painful software.
To anybody reading this: I highly recommend Pixelmator. It has a free trial, check it out.