You have to remember that the version of Longhorn you're downloading is in its first beta stages--it won't be anywhere near stable until the RC come out, which probably won't be for a while. I guess you could say that mileage will vary... anyways, just because you CAN get it doesn't mean you need to, or should. There's really very little reason other than to say "I did it."
|Vista is what was previously named longhorn right?
Yes. Microsoft renamed it so it was more consumer-friendly... Longhorn just sounds like a sexual reference or a Texas comment, neither of which says "Buy me!"
|is it worth installing it ? or will everything run like crap...
Even though I said it above, let me say it again: mileage will vary. As you can see, "Xaine" was able to install it fine, although what "fine" means can vary from person to person. Besides, there may be core features that he doesn't use that will crash the computer, as can be seen by m3x1c4nj3w's friend.