There's no good reason why Vista shouldn't have been able to run on 1GB ram laptops. It was so slow on my parents (new with vista) laptop that it made me want to scream using it. They upgraded to 2GB, and it was still pathetically slow until SP2 came out and fixed it. It works pretty decently now.
More than 2GB of ram, back when vista launched, for a consumer grade OS? Seriously? That should be a launch-blocking flaw.
I'm not suggesting that their underlying architecture was irretrievably broken, I'm saying that it just wasn't ready for consumers when it was released, and it thus deservedly acquired a bad reputation.
Clearly, there was something wrong with Vista.