So Photoshop CS4 is actually smoother than CS2. Huh.
15 years ago
I had been using the trial of CS4, and now that I've switched back to my own CS2 I've found that the tablet input is actually more clunky and wobbly. I didn't see that coming, honestly. And now that I've gotten used to CS4 I'm going to have a hard time adjusting. *sigh*
FA+

I noticed that tablet input got really sluggish right after upgrading my monitor. I went from a 4x3 tube at 1280x1024 to a widescreen LCD running 1680x1050. I instantly noticed that my tablet wasn't working right. I don't like Wacom's new driver, either, so I'm using a driver that's a few years old. Both drivers have the same sluggish response.
So, it might not be Photoshop. I'm still trying to figure it out.
And, yes, I like 5.5. I really don't know what they were thinking when they redesigned the GUI in 6.0 so the brushes are on a horizontal bar. With widescreen monitors becoming the norm, I don't see how any palette-based GUI can throw away so much horizontal space. Plus, the new brushes suck. I like to use the pencil tool rather than the airbrush/pen.