In about 40 trips through the G side, only once was the Immigration wait more than 20 minutes - but that time it was 70 minutes as a US citizen. I normally travel with a non-US companion and their wait time is often between 30 and 60 minutes, ranging to 3 hours once.
Baggage is excruciatingly slow, usually taking 30 to 45 minutes for Priority.
Customs has never had significant lines and only once have I been pulled over for a random check - and that only took about 5 minutes.