This really depends on what you plan on reading. I read a ton of PDFs: research papers, online manuals, natve PDF books and some books that are scans packaged as PDFs. My previous ebook was a Sony 505 but the screen size was too small to make this a practical reader for me. most PDFs out there do not support the "tagged" format that makes text reflow with the ebook posible. To make a PDF usable I would have to do an elaborate conversion dance of trimming and tweaking contrasts with some PDFs needing to be re- converted to landscape mode after several attempts at squashing them to fit portrait mode.

My eventual conclusion was that I needed an ebook with a bigger screen. After waiting and waiting for an apple tablet announcement I went with a kindle dx and it has been great. It does not hit all of the items in your requirements list (I keep the wireless off to conserve battery, the keyboard is almost never used except to jump to specific pages, and it's support of annotation is "weak" at best) but it is probably the best option out there for my needs.

My advice would be to start by deciding what screen size you need and letting all other requirements and feature comparisons flow from that decision.