This breaks with non-ASCII characters. Hard. The ö in my name becomes "ouml;" – some HTML encoding mangling is present there somewhere which really shouldn't be happening in 2013. There isn't even a reason to even use those entities in HTML. The ß in my street name manages to remove the rest of the street name completely from the output. I'd suggest you should test that data entered on the web site goes through unmangled to LaTeX and then use XeLaTeX to stay clear of Unicode problems (and also for better font support).

Fun facts:

  - ö gets mangled, ö (o and U+0308) results in "o?"
  - ü doesn't get mangled and survives in the PDF for some reason
  - When you return to the page all of ö, ü and ß are replaced by their HTML entities

Date formats could use at least ISO 8601 as well.

You can enter math mode and do fun stuff, but with people not knowing that it's LaTeX underneath this probably just invites fun errors when people use $ to mean $.

I've written my CV in LaTeX 1½ years ago (mostly because I didn't have a good-looking template in Word and was too lazy to build one myself) and I remember that I had to fight hard against moderncv to get it to do the things I wanted. It's not exactly flexible.