Sorry, Scott, but I disagree with your counting. DNN 3.0.0 - 3.0.12 had been beta releases for members of the developer's program only, who tried their best to provide testing results. The first public version of DNN 3 was 3.0.13 and sub-subsequent DNN 3.1.1 was one of the most stable releases in DNN history, IMHO. DNN 4 was a port to ASP.Net 2.0 and got stable very quick as well, there had been a hassle with some of the basic new features in DNN 3.3 (membership, file sync) which caused a few fixes, but this had been handled very well (kudos to the team - this happened before I got a CT member). This just demonstrates that there is not such a learning curve, as simple deducable from numbers.
Let's face the issues with DNN 5: there had been a number of internal betas and public release candidates. In fact, public contribution on testing and issues reported had been very few, which finally lead into a public release. Due to a number of issues reported, especially Charles has worked hard to fix as much as possible to provide the community with an improved version. Please be aware, even though the end user improvements of DNN 5.0 are few, there had been some fundamental features rewritten, like the improved permission model, which required more changes, than estimated in advanced, and showed up with some side-effects, which made it challenging to maintain binary compatibility in all interfaces. Kudos again for the development team, succeeding in this effort.
The team realized however, that there are improvements needed to provide a solid version of DNN 5 and therefore we are now heading towards DNN 5.1.0. If you encounter issues while testing DNN 5, please report it to the public issue tracker to help the team to make DNN 5 as rock solid as DNN 4.9.2. Thank you.