So good news and bad news:
We will start with the bad; if you haven't noticed yet there are now ads at the bottom of the forum. Being that this is a free service I don't have that big of a deal with it, basically they are using the ads to help pay for a new programmer they hired to help with new features. It is at the bottom of the forum and fairly small, so don't get worked up over it. Here is the full write up directly from them:
Now for the GREAT news. Over the past year or so Nabble hasn't had many features added because they have been working on a HUGE feature. Very soon they are releasing their Nabble creation language called Nabble Application Markup Language (NAML). This creation language will be fully useable in customizing our forums to however we want. Basically this forum will no longer have to look like every other forum. This customization is extremely powerful and is able to turn a forum into a website if we are so inclined. With this power means we can start creating some crazy powerful features with some ingenuity. Addition of XBL gamertags in profiles, more visible online users, more vBulletin like user pages, multi-quoting, fully customized forum look, etc
We have created a new stickied topic in Site Affairs for suggestions of features that you find at other forums or websites or other ideas you might have that you think could be useful. Keep in mind that there are limits to what we can do still, but they aren't as restrictive anymore. And PMing is still a toss up so don't re-suggest that. Make sure to read all of the other suggestions before you go suggesting more.