Gnu, definitely cook by temperature... and I'd always start with Cook's' guidelines, especially with beef, so you can get it exactly the way you want it.

You use the thermometer just before you think it's done, don't leave it in while it's cooking.

185* is an overcooked bird! I find them to be super-cautious with those 'implants'.

I don't like the digital ones... pain to replace batteries, too expensive to throw away. John's right: the dial-y ones are easily re-calibrated in ice water or boiling water if need be.

Dani