I posted this, going to add my system info:
Just some numbers: When I rez in my home in sl, using Phoenix 1.5.2, the frame rate is about 35 fps. When log off and relog at the EXACT same spot in Firestorrm 4.2.2 I get about 1 tenth the frame rate, yes, 3-4 fps. My home is on a residential sim that is usually deserted and a crowd is 2-4 people any where on the sim. Now going to somewhere like Franks Place in Phoenix, depending on the crowd, I get 1-5 fps. If I go there in Firestorm, I just CRASH as soon as I land --- IF I even get there.
Update: My computer is a Mac Pro (early 2008) Intel Dual Quad Core (Xeon, 8 CPUs), 16 GB RAM, on Comcast with 36 MB/sec download spead, Graphics Card is ATI 5870 1 GB Video RAM, running Mac OS X 10.8.2
More: I run Phoenix with ALL of the graphics maxed out on Ultra graphics setting and ALL custom Setting at Maximum and most important in Debug settings I have RenderAppleMultiGL set to TRUE, for multi-threaded graphics rendering which makes performance about 3 times faster than without it. Also Hardware settings have OpenGL, Vertex Buffer Objects Enabled, Anti-aliasing is disabled, anisotropic filtering is OFF, I keep my draw distance in the 200s, can still see far but not too far. Avatar Imposters is checked to render distant avatars as 2d only, this helps too. Hardware skinning is off as that slows my system down to a crawl and the same for HTTP get textures - very slow, so that is off as well despite claims to teh contrary it doesn't work for me.
Before the upgrade to Mac OS X 10.8 I used to get FPS at my home sim wtih Graphics setting MAXED OUT of up to 150 fps whic is insanely fast, that with Mac OS X 10.7.4 and at that time Firestorm would run in the low Teens FPS (at my home sim) . So part of the problem was an immediate degradation of Graphics performance upgrading the Mac OS from 10.7.4 to 10.8 However, even then Firestorm was unacceptably slow (as is Phoenix 1.6+)
I hear stories of people getting great performance with Firestorm, and even if I bottom out the Graphics settings it's still poor, so for my system, os, etc, Firestorm is still not an option and I need something to speed it up considerably. If it also means switching to NVidia Graphics I would do that as well. Not sure, as it's hard to find good information. Any ideas would help.