I have used the latest Firestorm for a long time, pretty happy with it. If you've got an updated viewer, it might be a settings/graphics card issue?
Derp, sorry- thought you were asking for help choosing a viewer. 's what I get for skimming. LOL
Make sure you've got the latest viewer first, if that doesn't fix it, check your graphics card and make sure you've got the latest drivers for it, I know there was a bug with AMD drivers a while back but I thought it was fixed with the updates.
I've heard that disabling "Hardware Skinning" in SL can help if you're still having issues, in Firestorm it's in the "Preferences", under "Graphics", the "General" tab.
"...to take truth for granted is not to know it. Truth not won is not possessed. We are not entitled to truths for which we have not fought." --- (Marauders of Gor, p.7)http://clockworkkitteh.blogspot.com/