Is it any less impressive if somebody creates a beautiful CSS site that completely falls apart at a different font size? I sure think so. I’m not saying a site should hold its visual design together if somebody bumps up the text 5 or 6 notches, but if they want it a couple points bigger, that’s fair. Hell, that’s the point. (No pun intended.)
We’re not designing print pieces. This is the web, and scalable text is one of the benefits. Users can, and will, change their text size. Now, if a user changes their text size to make your site more readable, and your visual elements cover up that text, it kind of defeats the purpose.
Which is more important? Fixed visual designs or flexible and scalable text. If a person builds out a site that’s less scalable, is it that they don’t know any better? Are they just being lazy? Do they value design over flexibility?
If scalable text isn’t important enough, what happens next month when you or your client decide that you need an extra line of content on the home page, but it won’t fit within your design? Don’t act like that never happens.