Five years ago I transited via Detroit. It was an awful experience and I vowed never to repeat it.
Unfortunately the demise of Zoom and domestic no-frills operators in Canada means that the likes of Air Canada now think they can charge what they like for their flights, so for that reason this Summer I found myself flying Northwest Airlines transiting via Minneapolis.
Yes, you still have to do a full customs and immigration clearance (including a biometric scan), yes you still have to pick up your luggage from the carousel and clear security again, but the difference was that this time it was handled quickly, politely, and efficiently. What's more, I didn't have to line up at a check-in desk, since there was a baggage drop and my boarding pass for the onward flight was issued at Heathrow, and my bag labelled accordingly. It was completely painless. The whole procedure from arriving at passport control to being in the departure lounge waiting for my onward flight took about 20 minutes! I wouldn't want to bank on this being the case all the time, and at every US airport though.
The only really unpleasant experience of the trip came at the hands of a particularly rude and obnoxious member of security staff at Heathrow, who was so nasty that I actually think he was trying to provoke some kind of hostile reaction from me.
In short, I would now consider doing it again, but unless there's a significant financial incentive as was the case this time, I would still go for the more convenient, less hassle-prone options.