Negative effects to 4s when upgrading to IOS 7?

What are all the negative effects that happen to your iPhone when upgrading. I had a little peak around an I saw a couple of things (slow keyboard and memory erasing) what are all the other problems and are they fixable, if so, how?

I've seen enough questions about iOS 7 update glitches the last day or two that I'm telling my partner who has a 4S to NOT update for a while.

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