A random strip selector could be useful, but personally, if I find a new comic strip that I like (new, as in new to me), then I'm going to go read all of the archives from the very beginning rather than grabbing random ones.
Of course, in the case of the aforementioned XKCD, the early ones are pretty bad (in spite of it becoming truly awesome later), but you'd be missing out on many good ones relying on random. And the early Dilberts don't have the quality problem that the early XKCDs do, so I'd just suggest you go to beginning and start reading from there.
I wish there was a feature enabling navigation to a randomly-selected strip, like there is in xkcd, for instance. Anybody else who thinks that would be good? I know many of you would've read every single Dilbert, but there are surely some, like me, who're recent addicts?