I am trying to understand the performance of jmonkey so that I looked at Bang! Howdy but the performance of the game is really bad. (when you click on a building zooming is really slow etc.) Is this related with jmonkey or are there any other situations about it?
The "opening scene" is pretty heavy… the rest of the game is ok. If you look in their forum you can see people are running it on intel chipsets and the like. Try running HalfLife 2 on one of those 
I am running it on a duel core athlon 3800 with Ati Radeon x200 graphics card. I think it is quiet fast but still the town scene very slow.
i ran it on a mac book pro with intels core duo each 1,8 ghz… and the standard graphics card and it ran without any problems and really smooth even in the opening scene …
must say i love it!
The X200 uses system memory, thus has a very crappy fill-rate. I think that's why the opening scene is a bit slow (it's got many pretty textures and all).
athlon xp 1700 with geforce 4ti here: the town scene runs very smooth