I applied on 13 Feb, got the approval notice on 29 Mar.
Chinese New Year was from 15-20 Feb. Also, I talked with a very helpful person at immigration who said my application was delayed by some inter-agency communication problems that should be fixed by now. So… maybe 4-8 weeks to get an approval notice.
The ARC took about one week to print after I found time to submit my physical passport to the consulate. I picked up the ARC at the immigration office 9 Apr.
Mileage may vary, but I wouldn’t expect egregious wait times.