FireFox going awfully slow

It used to be my most used, recommended, favorite, default and what not browser since I came to know about FireFox, but sadly I am seeing a noticeable degrade in the performance of FireFox since last few months and it has escalated to an extent that I have almost completely switched to Chrome. I am using FireFox 3.6 and the problem is so worse that it not only hangs itself but makes my machine hang too. My CPU fan sounds loud, and the CPU usage is not going below 100%, the problem worsens when a page has a Flash component/video playing. I am not sure what has gone wrong as this browser has matured through years; has it been overloaded with features? I feel this isn’t only my issue, as I see many people complaining about it. Chrome appears to work without any problems on my machine and I feel it to be lightweight, I hope FireFox too gears up to what it has been known for.. the fast and secure web browsing experience.