For those who want to be the "Fist boy/girl in the block" also do not get bother by challenges of advancement and know how to report a bug, and also like to have 100-500$ saved for now, it comes ear suiting to know that
Microsoft has Windows Vista RC2 available for download. Click on MS or
HERE to go to the download site if you like. Remember Uncle Bill won't give something for free or no reason. Well there is a reason he is the only human in history of mankind that has become a self-rich-man whose asset for the very first time is measured in terms of Trillion. So be prepare to be a Guiana pig if you are adventurous enough and you like to have the please of free first hand trial.
As pointed by other posters, would be a good idea to either install this on a new hard drive added / replacing you existing one (In case you want to go back to old OS or find the challenge beyond expectations), alternative is to have a second partition of your current HD for this OS but I don't advice that and definitely don't advice for a full switch at this time.
BTW the Vista unlike father XP, is going to be release at at least 4-5 entirely different configurations, completely different from one another i.e. not like XP home, professional MMC etc that where close relative of one another and be prepare to pay well for the fancy versions.