I went for an older model with a 4:3 ratio screen, bought from eBay: Thinkpad x61t. I don't like the new widescreen versions. I've installed windows 7 and an SSD disk on it and it runs surprisingly smooth.
The handwriting recognition in Windows 7 is amazing and usually spot on. For my PDFs I'm using
PDF Annotator which works really well but it will set you back $70.
The tablet will replace my current work laptop.