So I decided I wanted to try running my tank at 82F for awhile and see how it goes. I just bought a NIST-certified thermometer so I can calibrate client's thermometers accurately. So I check my tank - tank thermometer reads 80F on the dot. NIST thermometer reads 81.8F. So I guess I'm pretty much at 82F already.
So, I guess we should all take each person's listed temperature with a grain of salt!
I've also discovered something, from my testing so far (about 4 of each type), generally the digital thermometers are more accurate than the "mercury-type" thermometers.
NIST thermometer = best $40 spent recently.