Actually, the upgrade to version 2.5 had some pretty awesome changes, too! Seems about the same size step between 2.0 and 2.5 as 2.5 and 3.0. There is another program (Helicon Filter) which is in a similar (kind of) price range with Parallels, but they have a bit of a different pricing system, maybe it would do parallels good to take as an example: They charge $30 for the program. Updates are free, upgrades cost 60% (just like Parallels). Here's the difference: They offer another license for $60 which means all upgrades are free. This is worth it if someone would be interested in using (at least) the program's following two upgrades. It also makes it clear right at the purchase that while updates are free, upgrades aren't.
What about all the people that bought when they were offering free major upgrades for the first year. "This copy includes free Upgrade Protection for one year following the date of purchase, which entitles you to receive all major upgrades released during that timeframe at no additional cost."
What I said about having the program download version 3.0 may have been partially wrong. It seems that for a little bit after v.3 came out, build "3212" was actually (accidentally?) downloading build 4128. That is why I thought Parallels was almost forcing unwitting customers to upgrade. I think it is fixed now.