It's an interesting update, IMHO.  I haven't had any major issues with 4.5 so far aside from trying to figure out where the new stuff is and if the installed dynamic cloth function actually works since there's no request for a serial number.  Looks interesting, and for those of us who are lost in the minutae much of the time, it's nice that the lessons for learning the new version are at the bottom of the screen so you can select them.