To those running the iOS 5 GM on their iPhone 4. Is it slow at all? I'm trying to wonder if the new speed on the 4S is necessary. I remember my iPhone 3g was pretty terrible on the new iOS that came out at the time and the new speed of the 3GS was definitely great. But with my iPhone 4 right now, things seem as zippy as ever...does iOS 5 bog down an iPhone 4? Or does it remain smooth? Is a 4S really necessary if you never take pictures and don't care about the voice assisstant?