Jeff Freund:

"The easiest way to understand interface scalability is to think through a simple question about your content management system: what happens to my job and the job of the editors and authors when the amount of content in the system increases two-fold? How about five-fold, or ten-fold, or fifty-fold? It’s a question not many think to ask before making a CMS purchase, but it’s a revealing one. Many interfaces work very well with small amounts of content, but begin to break down when the amount of content in the system increases."

That's very true. We're pushing Movable Type's envelope at MarketingWonk, with 80 categories and 1600+ entries after less than a year. We'll probably customize the backend to fit our needs, and there's also the question of doing the whole site with MT.