I've been running boards for years (this currently being the biggest one), and if there's one thing I've found over the years, it's that if the board isn't constantly evolving in technology along with the people who use it, then there will gradually be fewer and fewer people using it until it's no longer worth the trouble of coming to anymore. I let too many of my things to grow old and stagnant and die, I don't want to let that happen to this one. This upgrade I just made (from 1.1 to 1.2) was not so much of a change as there was from vBulletin to XenForo, I thought it'd just be as quick as a version upgrade and it'd be the same as before but with a few extra goodies. I didn't realize before I'd done it that it would break so many things. This is the challenge with staying fresh.
Beyond the version number upgrade, there were supposed to be a number of improvements to handling spam. That's another department in which we have to stay current in order to stay ahead of the spammers. The older the board software gets, the better the spammers get at coming in and blanketing it with their crap.