Mine is capped at 30fps by OSR (Oblivion Stutter Remover). I count myself lucky when it gets that high. Course my Cyrodiil is loaded down with hi res textures, extra villages and NPCs, and lots of VWD (view while distant). As to low poly grass, I use such a mod. Depending on how low you go, the difference in quality is readily apparent up close. But further away it's not so noticeable or bothersome. You get used to it, then don't give it a second thought. In any case I find prefer the trade off of lots of free standing grasses at reduced quality over a lesser amount of higher quality grasses. Heck, I even added in some delux modded grasses (which receive the benefit of the low poly mod).