We have just switched to PunBB (see http://www.xgameproject.com/forum)... We had been running LokwaBB for about 3 years now. We eventually got sick of it as its features were limited to say the least, but most importantly, it was full of bugs (some of which we fixed ourself). The URL and IMG tags did not even work properly. PunBB is definitely an improvement. I didn't change the default style of PunBB too much because I like it when things are simple and efficient.
PunBB - It just works 