I've had no problems here. You might want to try out Microsoft Virtual PC or
VMWare to run a virtual machine and that way split your different dev
environments onto different virtual machines. It's especially useful with
beta software to avoid stability problems on your standard workstation.

Yes, they can coexist, but notice that VS 2005 is still beta 2, not even
final beta or release candidate, so it is recommended to make an image of
the hard disk with some 3rd party utility prior to installing, just in case
you want to go back later (or to use Virtual PC 2004).

I agree with both CT and Carlos that caution is in order. Although I have a
PC here (*not* my primary work PC!) with both installed and no issues (so
far), I read a report yesterday is a different group where the poster said
his VS 2003 menus disappeared after installing VS 2005. The track record
with Visual Studio betas, in general, is that the really nasty problems pop
up when an attempt to uninstall a beta is made to resolve an issue.
So, multi-boot, VPC, etc. would be the safest way to go if you don't have a
second PC handy.