Weird. Maybe a difference in desktop environment? I run Slackware (KDE desktop). Maybe that has something to do with it?
Around a year ago I recall reading a post somewhere about high CPU usage in lighttable view, but I can’t find it now. Perhaps it’s the same issue you’re experiencing? Simply moving the mouse around the lighttable does use a lot of CPU on my machine (~40% of one core) but it’s not enough to cause a noticeable slowdown.
Edit: and on reading the rest of the comments here it looks like someone else has mentioned the post I couldn’t fnd! 