Oh god, installing Logic is the biggest pain in the arse! We're going to be installing 9 at work soon-- i'm just glad i've only got to do it once, instead of 5 times like we used to!
Top Tip: When you've installed Logic, run Disk Utility (Applications>Utilities>Disk Utility), and perform 'Repair Disk Permissions', i'll help sort out any rogue permissions that might cause issues further down the line :)