We have a couple - they were neat little toys to play around with when we first got them - now they just sit collecting dust. I think the last time we used them was to measure the temp of the blacktop last summer on a really hot day.

Perhaps it's because I have a small collection - that I don't find them a really a necessity - they came in handy when setting up the racks but since then - not so much - I'm pretty good at reading the snakes - and if I want to tell the temp of the snake or enclosure I stick my hand in and feel it.