The one thing that tends to annoy me about Firefox is its weird stuttering problem. I don't know what it is, but if you leave it open for awhile with a ton of tabs open, it eventually has a problem where it sporadically accesses your CPU for some reason (I see around 12% or so CPU usage). The sporadic access usually occurs every few seconds, and whenever that happens, Firefox sort of "pauses"/stutters for a second.
I notice this problem a lot when I'm typing or watching a video, because the letters will not appear immediately or the video (not audio) will pause for a split second.
How do I fix it? Close Firefox and reopen it. Even having the exact same tabs opened upon start up, it runs fine after that.
I haven't seen it yet in FF7, but FF6 was really bad with cache management. The problem that I noticed is that eventually, it just had to sit there and monkey around with the cache
while it was trying to load a webpage. Doing this caused the site's load time to go from ~1s to around 5s, and you could tell that it was a cache-related issue, because my WD Caviar Blacks are quite audible (I moved my cache to my D drive).
Also, I tried to delete my cache one time while I was in Firefox.
Worst. Idea. Ever. It literally took around 10+ minutes just to delete the cache!
I dumped FF a couple of weeks ago and switched to Chrome because of the high memory usage/memory leaks of FF.
It's bad when you have 8 Gb of RAM and still get warnings about "high memory use."
Firefox 7 is a lot better with memory usage. I used to easily go over 1.2GB with just FF (PluginContainer would use more depending on any flash content, etc). I think the last time I looked, I was using around 800MB.