Windows 7 works OK and I'm using it. It's a popular view that a new Microsoft operating system shouldn't be used until the first service pack has come out. I've never subscribed to that view myself, so I'd say to install Windows 7 now and get to know it. I don't think you'll regret it. Updates are available as soon as the installation is complete.
If your present computer is a fairly old one, install the 32 bit disk (both 64 and 32 bit versions are included in the box). Older computer processors won't work with the 64 bit version.
Edit: You can get fair idea of how well your computer will work with Windows 7 by downloading and running the utility
found here.