Well, I'm back following my one week ban for telling one of the site administrators what I thought of him (wasn't a COD guy, and was unrelated to this game). It was definitely worth it, but from now on I suppose I will simply treat the individual in question as if he does not exist. Everybody wins.
Thanks all for your responses and advice in the meantime--I have read and utilized most of it. The latest patch has definitely improved things for my humble computer. By reducing the texture quality to High or Medium and turning the Land Shaders down to low, I'm able to actually play missions over terra firma that are smooth enough to enjoy, although I still get some stutters. I think one thing that improved performance for me was to turn AA off completely in NVCP. I have it set to 8x in the game options--something I might reduce, although I don't see much difference between 8x and 1x or any lower setting on my computer. I'll have to test it more.
The patch definitely makes the game possible to play and enjoy and really begin to appreciate all of the details at work.
Breathlessly awaiting the next patch, hopefully with the most glaring bugs repaired and perhaps greater performance enhancements.