Unfortunately i got the same problem, i had 38-45 with 800x600 resolution in 1.0 now i got 25-30 with 600x400 resolution in 1.1.
My PC specifications are 512mb RAM, VGA 5200 128 mb vram.
Even with these specifications my pc was running mta fine, with no problems.
As I noticed, all we have single core CPU, developers might optimize it for single core then.