I start around 122 tabs on news review mornings. depending on what tabs remain open, I start to see pauses. The browser will freezed for upwards of a minute before it figures out it's resources or whatever the issue. It's to the point now where I just go back to something else and check in with it in five to see if it response to mouse clicks again.

Now after skimming the monday morning news I'm down to fifteen tabs and 415 meg of ram consumed. No pauses yet so maybe FF5 includes some cleanup in the resource management area. We'll see as time progresses though.