iPhone 3GS getting really slow

Ever since iOS5 my iPhone 3GS has been getting slower and slower.

It can have a lag of like 2 seconds from simply turning it onto silent. It likes to crap out when reciving emails/messages; sometimes it does half the noise, then the other half of the noise at a higher pitch. Sometimes it might vibrate too early or late.

Loading the settings crashes sometimes. I have to wait quite a long time for some things like going into message threads etc.

Sometimes music sounds like a stuck record, which happens much too often.

Will a restore actually help? I've done restores before, never really found them to be that helpful. Just makes me waste time getting my homescreen back to how I had it.

Also I'm reluctant to get a new iPhone because the 3GS with iOS5 is about as useful as a 4S with iOS5 for me. Not planning on getting whatever comes next either. Might wait until my 3GS actally falls apart which will be a while considering I've had it for two years and it looks almost brand new.