I never use the built in Meat probe, because I don't trust the accuracy, because I haven't figured an accurate way to boil test that Meat Probe.
I've loved my 40"BT since I bought it. My biggest problem with temp swings was doing summer sausage when it would run up to 190 on the swing when I was trying to keep things under 180 and I was set at 170 - normally at higher temp settings it doesn't run that far past. But for my ribs, chucks tenderloins and everything thing else, the bit of swing has had negligible effect on the smoke. The BT is poor (regarding distance) but enough to reach my back office so I can follow my meat ITs without running outside. The accuracy of the meat probe vs my other probe has been close enough to be comfortable with it alone.....
Bear