I get that in Chrome in iOS 7.1.2I know what you mean, it happens to me sometimes. But this is definitely a nasty bug, it has nothing to do with the general speed and responsiveness of iOS 8 on your iPhone 5.
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I wish I could do that....I have over 130 apps on my iPhone5.I did a clean install and did not restore from backup. Its buttery smooth. Works really well. No stuttering or crashes.
I backed up my photos to an external hard drive and didnt need anything else backed up anything other than contacts. Contacts are restored when signed into the iCould. I re-installed all the apps and set up the email. I am good to go.