Yes. The only issues I've run into involve desintallation. When you want
to deinstall either, you need to deinstall both and then reinstall the one
you want to keep.
VS6.0 and VS.NET (2002/2003/2005...) should be able to co-exist safely.
However, since VS2005 is still beta, no one can guarantee you it is 100%
safe. To install a beta product, you are supposed to be prepared to reformat
your hard drive later if you cannot remove it cleanly (it happens so often).