Pretty much - I can't say it's zero performance hit with it installed, but it's likely to be very tiny and essentially impossible to measure.
As the more programmers start to use the .NET technology, you're likely to see more programs that need it (especially when Vista comes out, because .NET framework will be a key part of Vista that is automatically installed - rather than an option like on XP).
If you keep it installed, it'll cause you less problems than if you uninstall it, and then have to install it again at a later date because something needs it.