I have and use both and I really really really like playing with the tempgun!
The only problem I have with the temp gun is that when you point it a a heat source (heat lamp for example) the temp varies depending on how close you are to it. But if you are measuring normal temp things, it is pretty much the same no matter how far away you are. (But the only time I ever need to measure say, a heat lamp, is if I'm playing with the tempgun, so its not even a problem!
Don't get me wrong, measing your ball pythons's hot spot is not near hot enogh for there to be a temp difference depending on how close you are.
^^^^^^^You can probably disregard the above, I just decided to ramble lol^^^^^^^^