Well, I would go ahead and install win 7. It'll be good till after the public is able to
purchase it. As long as it runs ok for you I would keep using it. I would however invest in a product called Acronis and an external hard drive to back your entire system
at least once a week. Remember, it's a test system so if you put your production, valued data on win 7 you should definitley have a backup plan. I backup once a week.
I would also set Windows update to inform you of new updates, but not to install them so you can decide whether you need them or not.