iPad 2 MC987LLA ? DON'T UPGRADE!!!
iOS 7.x to iOS 8.4.1 brought my iPad to its knees: Nearly everything moved so slowly that iOS 8.x rendered my iPad unusable.
iOS 8.41 to iOS 9.0.1 restored pre-iOS 8.x performance to this very same iPad with no other changes.
iOS 9.0.1 to iOS 9.0.2 has once again killed iPad performance so badly that iMessage and email apps often just fail to start. Hard Reset (Home and Start button) does not improve things.
Temporary success with iOS 9.0.1 fooled me into thinking Apple had actually improved iOS to the point where I could resume regular upgrades. WRONG!!!