HeloPait,
There never were any compatibility problems with the C4480. Some people had some issues where the upgrade process left things in a weird state, or they were trying to use HP Scan Pro or HP Device Manager, which don't work under Snow Leopard, but the device has had Scanning, Printing, and a Utility from Day 1, and there has been a full solution posted for a while now too. So for the Photosmart C4480 at least, I would say you're pretty safe.
And if you do run into any problems, there are plenty of posts here, especially in my FAQ thread, on how to re-install things and get them running. Not to mention, I am actively participating in these forums trying to make sure everyone is working.
Just trying to help.
Andrew