Windows 7 is much better at handling driver installs than its predecessors,but I am still a little old school when it comes to installing drivers or software and I personally think it is better to load one driver at a time and re-boot after each one. Although it does take longer, from my experience it also seems to improve the way the OS handles the drivers and there is less risk of corruption during the install.
Another reason for loading drivers and other items of software, one at a time, is to help discover if there are any issues. It is easier to locate a problem if you are only installing one thing rather then sifting through 4 or 5 things if something goes wrong.