At this point, I have but one unfavorable issue with IP.Board 3.x...
The lack of proper lightbox usage on resized, hyper-linked images.
I submit the following example:
http://community.invisionpower.com/blog/2553/entry-3542-member-related-hooking/
Mind you, this is a blog entry. But, hyper-linked images act in the same way on the forums as well. (Too lazy to search for a post example too. :P )
For starters, at least in FireFox, the images are often not resized the first time I visit the page. I have to do a screen refresh in order for the images to be nicely resized and not full size (half hidden under the content blocks to the right). The real issue, however, is that once they are resized, clicking on them only expands them inline instead of launching them in lightbox. Given the fact that it happens on my forums as well as here I can only assume this is desired effect, for some reason, and not a bug.
Having them launch in lightbox like thumbnails and gallery images do (ex: ) would be much more desirable, IMO.
It's probably simple enough to take a look at the template bits and code this to work on my own. But, I'm putting it out there because I really can't see why this isn't a built-in feature.
Thanks for listening. :)