[sheepdog]

Had to jump in on this.. I have gone through board hell in the last year...

Here is what I have noticed..

Yabb/UBB...
just does to seem to have a lot of functions I wanted. So I never installed them. If I need mroe than 5 patches to get what I want, its too much. Things can get buggy.

Ikonboard...
While it seemed nice, it just was not going to work for me for various reasons. Corrupting the DB on instal is not a good way to start though. I did like it though for the 2 weeks I ran it.

PHPbb..
I liked., I really did . Worked great.
However, it was VERY taxing on ther server. Its a very inneficient forum. It brought down the server too many times.. Which is why I now run Invision. Like someone else said, once the database hit around 50 megs, things started happening.. If you run a small site, this is the board for you, really. Just watch your resources. As soon as you start to grow, skip straight to VB. Really.

Invision.
Great prog... Kinda Dropped my resources compared to PHPbb (75% bandwidth, 15% cpu approx). Too bad it has loads of small problems. I could probably fix them, but frankly, I do not want to spend anymore time on it. It will hold me through untill I can get a copy of VB going. I think its troubles are holding back my site at this point.

VB...
I only got to test it out, it was not my board. But its less resource intensive, more stable, and just plain works like it should. I have seen some massive sites running it with no trouble.

I also tried some other less known ones, but most were more like a Beta than a release.

I too hate the thought of shelling out that kind of money, but after the problems I have had, if it works like I know it will, its worth it. Its a drag having to constantly fix databases, and errors all the time. Frankly, in the end I think I will be kicking myself for not doing it sooner.