This is a discussion on goodreader for ipad vs iannotate vs PDF expert within the iPad General Discussions forums, part of the Apple iPad Discussions category; Any recomendations?...
There are lots of recommendations on these forums......have you used the search function?
It depends on what you want to do I guess but GoodReader is one of my top 5 iPad programs.
In brief, there are a lot of good PDF apps available. It helps to seriously consider what your needs are before deciding on a purchase.