Nonabelian,
here's a thorough review of how the t1 handles pdf files. Think it covers it quite well. You might want to look into it if you're considering the sony. But it also points out the limitations, so after all a kindle DX might be a better choice... up to you!
Update: Forgot to actually provide the link:
http://www.the-ebook-reader.com/reader-wifi.html
I've decided to wait a bit before I buy one, however. On the sony forums many people are reporting that it frequently freezes or crashes. So it might be wise to wait for sony to fix this bug first.