Important: if you're buying this just for Urkel, bear in mind he doesn't appear until episode 12. The writers originally meant for him to be a one-time character for that episode, but he turned out to be so popular that he became the focal point of the show.
Not that the lack of Urkel in the first several episodes is a bad thing. In fact, it's kind of refreshing. Before Urkel's constant one-liners ("did I do that?") and physical comedy (how many times can he break a window or fall onto a coffee table?), the show was really character-driven and actually focused on, well, family matters.
This is one show that jumped the shark hard in the later seasons, but Season 1 is full of nostalgia and warm humor. Cheesy? Yes. Worth watching? Yes.
One note: the DVD packaging itself is kind of shoddy. Not sure if mine just happened to slip past quality control, but the plastic is really brittle, and the little spindle where you're supposed to snap the disc back into place pretty much broke off, so the disc now rattles freely inside the case. Not a huge issue, though. Worst case scenario, put the disc in a paper sleeve or in one of those giant, zippered CD albums everyone had in the nineties.