They all seem to have an accuracy of +/- 2 degrees, just like the digital thermometers many people use. Personally I don't use them except to check feeder rodent temperatures.
I had this one for awhile, it works pretty well. It does have a 1:1 ratio so i got concerned about the temps at the back of the tubs and ended up getting the pro exotics PE-2:
I have a expensive one a cheap one and a mid priced one all the same specs (+/-2ºF) and all read slightly different (0.4º of each other) and slightly off (about 0.8º wrong). They are great quick check tools and fast scan tools they are not the most accurate or consistent of tools as long as you understand the limitations they are great.