If you're not sure how much you will use the software then getting EQ5 and get the upgrades later might make sense. But if you like drawing your own patterns, then maybe getting the newer version makes sense. I would read what the features are of newer versions are on the website and see what interests you.
I'm happy with version 5, I can draw or pick from the library the designs I want. To have more block designs, I purchased Barbara Brackman's Encylopedia of Quilt Patterns and with the drawing features I can draw any block that's in the book. I don't use the fabric library at all, I may plan what color I would like to use in a quilt, but think its better not to be so set on what color or print because I might not be able to find it. There might be newer features on the upgrades but haven't been convinced that I need them. Chris