Well, I must agree with the people here. The most atttractive thing of punBB is its lightweight. It provides all you really need to host a forum, and most of the things you'd like to have you can easily implement.
I use it as an extra value to my site, where my customers can discuss about bugs and request features or simply express their opinion, and it was peanuts to integrate it. Besides, I've learnt a lot of good programming techniques browsing through most of the code. If I want phpBB or IV or whatever, I can go and get them. The minute you start competing with the others, you're running a competitive race, that you're likely going to lose unless you've got a really good supporting team.
So, due to its flavour, punBB is the best choice for me. If it changes completely, it won't be. Don't misunderstand me, flashy boards are nice to see, but they serve a different purpose. If I wanted to attract people, I wouldn't be using punBB (no disrespect meant) just as it is, but I'd be adding lots of mods, or simply get another package that is easier to install and has them allready.
Maintaining this board simple and at the same time updating the mods is much more work than integrating them and forgetting about them, but with a little work from the user (and don't forget we're talking free products here) you can customize it as well.
Oh, well, that's so much for ranting, each position has its advantages, so I guess we'll all be of different opinions... which is much better than the opposite
Marc