I just asked a question about temping a few days ago as my temps seemed to see-saw. I'm using an ear thermometer and apparently that is a no-no because supposedly they're not very accurate. As you're not supposed to swap thermometers mid-cycle, I've got to stick it out with this one.
I've found (after conducting a very scientific experiment where I kept testing with the ET and a normal digital one...) that my ET is actually pretty accurate, but only if I use it in my left ear! Seriously, my right ear gives readings that would have me unconscious from hypothermia! I'm not sure why that is, and can't say I care.
My temp really DID fluctuate wildly at the beginning of the cycle, my chart looks like the "rocky mountains" according to Fertility Friend (sign up for their free trial if you haven't already done that!) but apparently that has to do with recidual progesterone or something. Now that the see-sawing has calmed down, it really does seem that my 6AM temps are very low, around 35.5. Just for fun, I've been testing again at lunchtime and my temp then has been 36.4 to 36.5 I'm hoping that means that my temps are stable enough for me (or Fertility Friend) to detect ovulation once it happens... I'll let you know in a few days!
The problem is, as I understand it, not so much with the difficulty of getting an accurate temp (as I found) but more because of the shift in temp can be as little as 0.2 degrees (C) and therefore it would be easier to detect on a BBT that measures degrees to .00 of a degree. So, I guess it might depend on the individual. I'm hoping that as my BBT seems to be pretty low, I'll get a bigger shift in temp (and in any case, as my ET does measure to .0 of degrees, it should pick up a 0.2 shift.
Sorry for the long answer!
(Oh, if your ET does measure .00, please let me know, as I far prefer the ET as they're so quick and easy!)