Well yeah, that's what I'd expect. But it was bad, even for pre-release. I specifically remember people with top of the line systems at the time having issues running it..
Which is really what surprises me about 8's beta, how well it runs. I even saw someone running it on a Pentium 4 system.
They are two completely different scenarios. Longhorn was a whole new kernel update/build, graphics redesign etc that turned out crappy in the form of Vista. Metro is almost like a shell environment running on top of an existing stable kernel. Speaking of which, have you even used Metro? I actually have the most powerful tablet in the world sitting right next to me with Windows 8 Metro on it. I've been actively testing it for the past 3-4 months and I can say that there are plenty of issues with the Metro UI:
Lack of consistency with how the UI reacts to attempting to rearrange app icons.
Issues with moderate flick gestures / multitasking movement between apps. The app freezes up, metro freezes up, or the app doesn't let me out back to Metro.
There's something lacking that Microsoft needs to figure out between filling in the gap between a touch-screen (Metro) oriented application and going into classic applications.