I still haven't gotten a thermometer for my new aquarium. I've got a stealth heater and right now I'm just assuming it's maintaining the temp I have it set it.
Everytime I'm looking at fish (there are a lot of places around here with fish), I look at the thermometers, and they're always terrible. Whether it's a $1 thermometer or a $5 thermometer, there is usually at least a 5 degree difference between a single brand of thermometer on a single peg. I was just in a store today, and looking at their more expensive thermometers, one read 68, two read 72, one read 73.
It actually makes me think that those plastic stick-on thermometers might be more accurate than the POS glass ones these places sell. There's just nothing that looks like a quality thermometer. Some of the LFS
have $30 digital thermometers that have a clock in them, but I don't have any desire to spend that much (or to have a clock on my aquarium).