Flinger -- the memory usage issue is not really an issue except for the fact that the garbage collector does clearly have non-trivial problems since WoW 3.0
That said... my top priority now, aside from finishing the detachment of the configuration data from the layout engine, is cleaning up nUI's memory usage to reduce the load on the borked garbage collector.
However... it is *very* important that you understand the problem is *not* nUI. This post is a perfect illustration of the issue...
http://forums.worldofwarcraft.com/th...03572404&sid=1 -- raiders everywhere have been having endless FPS issues even in otherwise "lightweight" configurations.
Do know I am working on improving nUI's footprint.