I just bought Fusion 4 two months ago. Was using Fusion 3 for a long time just fine... got a new retina mac and had a few issues with it, so got 4 and it mostly fixed them and I was content.

Now 5 comes out, seemingly has better retina support, and I'd have to shell out $50 again. No thanks.

Each Fusion release is less and less compelling for the most part. Fusion 4 was "built for Lion", yet I used Fusion 3 on Lion exclusively until June just fine.