The latest LL Linux beta looks like it fixes the memory leak that has been plaguing me for some time. (It also includes some of the UI changes that people have been talking about.) The client was endlessly allocating RAM for a .WAV file!
BUT... it still suffers from SH-2306, i.e. the screen goes to near solid blinding white when you turn on shadows. (I was too overjoyed with the RAM usage staying under about 670 MB in a session of nearly an hour to notice the lack of shadows, I guess.) That bug is now labeled as dependent on the bug of the SL client using deprecated OpenGL calls, so I guess when that's corrected, I will be truly happy. In the meantime, maybe I can plead with the Firestorm people to correct the memory leak, and have the best of both worlds. :)
UPDATE: Sahkolihaa Contepomi kindly suggested I try the testing client linked to from the SH-2240 JIRA entry. Sure enough, it works with shadows turned on, and after the better part of an hour wandering around stores with several SI standard posterior-loads of textures, RAM usage had slowly increased to around 2.2 GB, whereas the memory leak that's been clobbering me would have grabbed over 3 GB in mere minutes. So... I am happy--and even better, there's word on the Phoenix/Firestorm blog that a new Firestorm version is near completion. I hope it will include the memory leak fix!