Overall performance I'd say keep the phone clean.
Don't add unnecessary apps, especially if you're not going to use them.
As far as the battery savers are concerned, I find them to be total crap. Even Juice Defender. I tried it, wasn't too pleased with it, when my friend asked me about it I told him to try it out himself. He ended up deleting it after a week also.
In my opinion, the phone came with a lot of bloatware, adding more stuff to optimize it is not really helping.
If you really find your phone to be slow, then my best advice is to root it and take it from there.