Ive also been testing it for a long time and am Vista-certified [Microsoft's new program for people in the tech field]
That being said, I would consider myself fairly knowledgeable about MS Vista. I am not 100% sure if I will upgrade, regardless if I do, it won't be an immediate upgrade. I was not impressed but a lot of things it had, and the biggest factor is that it doesn't really add anything that makes me desire it. As Wojtek mentioned, the functionality of many things has not changed much, for better or for worse depending on how you look at it. I would gain nothing from upgrading, except some features I don't need, a pretty style, and slightly more stable environment. My XP machines don't crash anyway, so im not too concerned with an immediate upgrade.