I have been using Q2A for a very little time but i feel it is a powerful yet very simple to understand script. There are many in market written on different platforms from Python to RoR etc. But having Q2A on PHP and mySQL makes it reach much larger given that these 2 technologies are still de-facto when it comes to finding the host. However, there are few things which I believe we can do better.
1. Faster development
2. Modern Look and feel
3. Mention against each plug-in theme the version of Q2A it supports
Not that I am criticizing, but I am looking for an opportunity to make it much more better.