latest drivers and at resolution slightly higher than yours (about 20% more pixels than1440x900) ultra 4xAA
assuming scaling with pixel count you avg fps with same settings would be 63fps (just an assumption, probably a bit off)
if you tone down AA or drop to High settings you should be able to hit quite a bit than 60fps avg
If you disable MSAA on BF3, the 7850 can run it on Ultra just fine at very high fps. I was gaming tonight at 1920x1080 and getting 50-90fps depending on complexity of the map (in multiplayer). With MSAA on, you should still be able to get 50fps at 1440x900 as that's a pretty low res.
MSAA smooths out some textures, but it also puts a foggy look over everything. I actually like it better without.