The automatic installation of drivers is still the same afaik - first check online for latest version if available, then check the local ("in box") driver store.
It doesn't trawl the whole disk or other partitions for possible drivers to my knowledge (that would be a very slow process and very rarely useful - plus tricky to handle situations where multiple driver files might be present in sub folders).
I too was impressed with how smooth the installation went on my home rig, only the RAID controller driver (which I don't use) doesn't have an immediately available driver.
I've also had use of the "check for solutions" feature in Vista, where missing drivers are later added to the store and the system provides the link to download them directly from the manufacturer (e.g. Intel).