I have a 505 and a 950. I'm really happy with my 950 for this very reason, but I did have some success converting PDF books I really wanted to read.
It was a little work, but I would use calibre to convert the PDF to an RTF. Then I used Word to do some fancy search and replacing. I could usually get rid of the all the dropped paragraphs and sentences and easily get rid of any annoying headers and footers. Sometimes I still found some weird things like non-capitalized names etc. Usually I could take care of those as well.
Once my RTF file looked reasonably good I would convert it to LRF or EPUB.