i have never used any sort of temp controller other than the daisywheel and the draft door. i've never had any problem whatsoever maintaining temps in the big green egg.
i am waiting for a fellow forum member (woodpelletsmoker) to make his new wireless thermo though. i have wanted a reliable one of those and the last two i bought (sunbeam brand, i think) have been as horrible as you could imagine.
Large BGE, Small BGE, Mini BGE, Weber 22.5 OTG, yellow thermapen, pink thermapen