Corrupt OS a effect?

Having been a long time Windows user, I know periodically you have to reinstall Windows every year or two. Some Windows users say they don't have to do this, but I certainly always have.

Is this true with Mac OS X? I've been using it for a week now, and wonder what the effect is of installing programs, deciding I don't want them, and then uninstalling them. With Windows, this could lead to registry entries that should be deleted, but were not during uninstall, and DLLs that also didn't uninstall, cluttering the hard drive. Eventually the OS slows down and gets sluggish.

Does Mac OS X suffer from this?

No. OS X, as a derivative of BSD (itself, a UNIX variant) was designed for mainframes that run in mission critical environments. It was intended to run 24/7/365 and never need to be reinstalled. The OS prevents major system directories and files from being modified. There is no registry. Worst case scenario is that you may have to create a new user account and delete the old - but even that's a pretty rare event.

Windows can accumulate cruft over time, particularly in the registry, which will eventually make it unstable or slow. It's not a question of "if" it needs to be reinstalled, but "when".