There are many improvements in 4.5, including the browser, calendars, address book, etc. You will need to read one of the very many 4.5 threads here to discern them all. I don't have a complete list.
Has anyone tried installing this to a 8800 locked to Rogers? Any reason it wont work?? I would really like to get my 8800 up to 4.5 but dont want to brick it.