It's still a little buggy, isn't it? Sometimes I can jump two blocks high, sometimes I can't. I tested it a little:
It seems to depend on VSync and the resolution. With VSync off and at a lower resolution the jumping works correctly; with high resolution I can sometimes stand on walls or even glitch through blocks. It's probably partly because my 2006 laptop is pretty weak, but it's never affected the correct working of basic movement so far.