Parent is correct, and it's not placebo. Disabling swap on OS X usually results in a dramatic improvement. People unfamiliar with the poor memory management of OS X tend to become personally offended by this suggestion and often start explaining how swap works (usually incorrectly). The reason is simple; it swaps when it doesn't need to, and swapping is much slower than accessing memory. For what it's worth, I've been running this way for years.

Yes, I know how swap works - I'm a kernel developer (mainly FreeBSD, but I have experience with most mainstream desktop kernels, including Windows). No, it's not dangerous to run without it in 2013 if you have enough memory.