The size of your page file isn't a sign of a performance problem. What matters is how often your paging out and in between disk and memory. That will result in a huge slow down in human-perceived performance.

The OP (and others, including myself) have observed a noticeable drop in the delays caused by frequent paging in and out. I checked and my pagefile is the same size as on Lion. Perhaps ML is still paging frequently, but if so, they've found a way to do it so that I'm not noticing it. Everything just feels faster compared to Lion.