LampCMS probably has the same functionality, but on first glance it actually looks alot nicer than Q2A. I especially like their user pages (e.g. http://support.lampcms.com/users/12/snytkine
). I've found it nearly impossible to customize Q2A's user/member pages. They look horrendous and design is ultimately important in building a Q2A community.
All in all, the main problem with both Q2A and LampCMS is that the developer community is tiny around these programs. So you are stuck waiting till the developer actually adds something. With Q2A it seems like there is one person, Noah, who writes plugins.
Q2A is a great piece of software. I just wish it had some better design and usability features added, and I hope some developers get involved, so that there more plugins for some necessary features.