I have used Mozilla / Firefox for what seems like forever, but 3.5 just is sluggish for some reason. It might just be my installation, but ever since upgrading

I have used Mozilla / Firefox for what seems like forever, but 3.5 just is sluggish for some reason. It might just be my installation, but ever since upgrading to 3.5 Firefox is really slow starting up. Now I've switched to Chrome but I do miss the Flashblock plugin.