I have also been having this problem, and also traced it back to being an issue with HP printer drivers (I'm using an A4 print size). If a printer using the HP driver is set as the default printer under System Preferences/Print & Fax, then the slowdowns occur. If you select a printer using a non-HP driver as the system default, no slowdowns occur.
I have outlined the various steps I took to find this in this thread on the Apple discussions site, including an instruments trace that shows the CUPs calls during the slowdowns. The message below links to the useful posts
<http://discussions.apple.com/thread.jspa?messageID=10308110#10308110>
Other users have since confirmed the HP driver involvement. Hopefully this extra info will lead to a fix,
J