[manicdee]

It's also to do with Spotlight re-indexing the contents of the phone. Every email, every contact, every web page still in history, etc.

There's some "optimisation" happening too, as bits are shuffled around so the most commonly used parts are fastest to access.

This applies for OSX as well as iOS. After upgrading, just wait an hour or two and everything will settle down. The impatient will simply have to cope with slower speed since the device is still sorting itself out.

[chucknelson]

Agreed - after a restore usually an iPhone will get unusually warm, I assume because it's doing this indexing and such. I don't recall if it happens after an in-place upgrade, though.

I wonder if Apple will ever add some sort of indication when the indexing, etc. is happening, so users don't become frustrated and/or wonder why their phone is hot all of a sudden.