In my mind (beta tester & early adopter) there isn't much difference between v4.5 and what I would call v4.4 SU 7. For the most part, Sage just threw their final extended solution enhancement pack at it, added a one user license of Sage CRM and called it a full release update. Not many WAD fixes but there are a significant number of bug fixes (325 by my count. I really don't see anything to hold back for. V4.5 allows you to install over the v4.4 folder, so there isn't a lot of issues with relinking file attachments. If the client is a heavy hitter with SMI, you are out of luck as they haven't released the v4.5 version of SMI yet. For the smaller installs, I say go for it.