I have run a digital photography site for several years. Two urls pointed to the same site.
I wanted to make the site into a digital photography community site with features like blogs, comments, tagging, etc.
So I broke up the URLs. The old site used HTML, a little Javascript, and Dreamweaver.
http://www.thelightsrightstudio.com
That site is still around. I am migrating all of the free tools, tutorials, etc. The site will remain as my personal gallery.
The new site is written in Drupal 5. I purchased a template from Drupal Shark and modified it.
http://www.thelightsright.com
My concern was site performance. I serve video. Long videos upwards of 45 minute to an hour in some cases. 800 x 600 with CD quality audio. I had heard (and saw stress tests) that indicated Drupal bogs down after 40 or 50 simultaneous users. I heard PHP was slow on IIS. I heard there was no mod-rewrite for CleanURLs.
First decision. Dedicated server. Colocated. The site is using a quad core server, 2.5 GHz, 6GB of RAM. 1.2 TB of disk space. Mirrored. Single dedicated 100 mbps connection currently. Four more connections available. There is also a socket to add a second quad core processor.
Second decision. Microsoft Server 2008 Web Edition. IIS 7.0, added FastCGI and Zend to improve PHP performance, enabled server caching, added new module from Microsoft for URL rewriting.