When NATS4 came out I didn't like it and now I love it ... as an affiliate.
Stand Ahead is a program that recently completed a successful and seamless migration from 3 to 4. They did not lose any stats and you do not have to go anywhere to get historical stats. They also have the selectable 3 skin for those affiliates that are not interested in all of the extra features that 4 has over 3.