Speed Freak is probably one of the more unfortunate names to give an application, but from a developer called Big Fat Stinking Software, it's clear that branding and marketing is not a priority.
Speed Freak is actually a very useful tool for prioritizing certain applications to receive more CPU power in order to make them run faster and with more stability. At specified intervals, Speed Freak reprioritizes applications so that the the most active applications get more processor time than background applications. It has a Basic and Advanced mode. In Basic Mode all you have to do is specify a percentage of resources to allocate to front end applications. In Advanced Mode, you have control over how much to allocate to front end, back end and the frequency you want it to check.
This is useful because by default, all processes in OS X have equal priority, which is a bit illogical when you think that some applications - such as Firefox and Parallels, are obviously going to need more than small apps like Adium or Skype. Speed Freak overides this limit using the Unix 'renice' command.
The developer highlights that Speed Freak does not affect graphics card performances, and will show little or no increase in 3D gaming speeds. Download speeds from the Net won't improve either but the time pages take to load could be sped up by giving more resources to your browser.
Since OS X is not designed to re-balance your system like this, you may experience some instability issues with Speed Freak, but overall it seems like a remarkably effective application in the short term.