It will probably be a little slower but all the minor updates since the original release of iOS 8.0 last September have done quite a bit to resolve some of the earlier problems. My old iPhone 4S is running quite well on iOS 8.2, with no major problems. If you decide to update, you may want to consider updating through iTunes on your computer instead of OTA as there is a better chance of a problem free update. Make sure to backup your iPhone before starting, then use the restore function to erase the phone and update to iOS 8.2. Once updated, you will be given the choice of setting up your phone as a new phone or from the backup you made. Choose the backup,and everything on your phone before the update will appear on the newly updated phone. This includes app data, game progress, contacts, messages, etc.