Tegra 2 supports CSAA instead if MSAA...i can't test it for obvious reasons but it should be supported.
Edit: Performance impact depends on the gpu. On my Nexus S, performance is quite good. However, it doesn't really look like plain multi-sampling to me, because it also shows some effect on texture content (i.e. it somehow blurs transparent edges (fps counter) for example), which multi-sampling alone shouldn't do.