If we assume that you sometimes fly back to IAH from elsewhere, CLEAR could be worthwhile if it prevents you from missing just one flight, but you need too assess your own attitudes toward risk and your tolerance for suddenly finding yourself unnecessarily in a very long line. However, I'm posting from the perspective of someone who not only gets CLEAR for free as a DL DM but also is a hub captive where the hub now has CLEAR (as well as the DL terminals at a number of major domestic airports), so for me it's been great.