Try updating to beta12.

Thanks for the quick response, and thank you for notifying of the new update but unfortunately I'm still facing the same problem. I'm currently 70% satisfied with firefox, but if I could solve this problem alone I'd probably be 90% satisfied.

Open the Windows Task Manager and see what the processor load is when Firefox is sluggish.

You could also check the processor load while you're in the Firefox SafeMode.
Help > Restart Firefox with Add-ons Disabled...

What do you mean by processor load? And there is no specific moment when it's sluggish because it's been sluggish for every single moment.

The result is still the same with add ons disabled. Like I mentioned, it's been like that ever since I first installed Firefox with no add ons installed.

It's strange because my laptop is a not an old laptop. It's a laptop used for Gamers playing high end games, which was bought brand new.

Having the same problem. After LOTS of clicking and experimenting, here's what I think I've found:

1. The tab performance when not maximized was much better.
2. Outside of safe mode, the Add-ons tab appears to be FAR more sluggish than any other tab. No specific extension or plugin is slowing it down. It simply lags.
3. Switching between Mozilla sites seems to be slightly sluggish compared to switching between tabs for other sites
4. Disabling the "Tab Utilities" extension (ithinc) made the performance when maximized equivalent to the non-maximized performance. This leads me to believe that the difference between the two is caused by this plugin. The Add-ons Manager tab, and Mozilla sites were still relatively slower.
5. Disabling all other extensions offered no additional improvement, but, strangely, starting in safe mode did. While inside safe mode everything is super snappy.
6. I have a sizable list of extensions, including a large number of disabled extensions (most of which I can't "remove" because they are from 3.6)

The time periods on #5 are very small, on the order of perhaps 80-100 milliseconds. Just long enough that you do a double take and wonder if it was really slower, or just your imagination, but then when you compare against changing tabs in chrome, it's clear that you aren't crazy. There is no noticable difference between safe mode and Chrome, but there IS between non-safe-with-everything-disabled and Chrome.

Is it possible that this is caused by some sort of broadcast to all plugins about the tab change? If so, could this broadcast be completed asynchronously, or else AFTER the tab switch? This is really a perception issue. To feel "fast" to the user, the click should result in instant visual feedback. If my plugins want to know something about the change, I'm satisfied with letting them wait until after I find out about it.

More digging. Discovered that disabling hardware acceleration resolved all the remaining issues (including the discrepancy between performance on certain tabs). I'm using a middle grade Win7 laptop 6 months old, but I can't say that it has an excellent GPU. Still, it seems odd to me that allowing hardware acceleration would actually hurt the performance.

Possible fix: Change the HW option to a tristate: "Use hardware acceleration if it is available" - "If it will improve performance"|"Never"|"Always". Make the first selection the default, and use some sort of benchmark to detect when hardware acceleration may be hurting performance.