Its the way microsoft have packaged the installer and simplified the process, its progress! Also win 7 has so so many more drivers available to it for installation as well as if its connected to the net it will get them automatically if they are available.
Win 7 install 30 min on 7200 hdd
Win vista 42 min on 7200 hdd
Win XP 1.20 hr on 7200 hdd then updates 2+ hrs lol