I've done two (a practice and a real run).
On the practice, one of the two slides planned for use failed to inflate so we took about 3 minutes to get 140 well briefed, calm, professional, adult military personnel out of the remaining door. No injuries but little confidence in the kit.
On the real run, 38 pax and 9 crew got out nice and quickly - although it would have been quicker if the firecrews had not tried to put an aluminimum ladder up to the front door. Again, all military personnel, all adult and all had 25 minutes to prepare.
The circumstances of the real evac were a double engine failure and fuel leak on a 4 jet airliner, with fuel dripping onto warm brakes after the emergency landing. No actual fire but the risk meant we took no chances - but again, as there was no actual fire, the lack of panic helped facilitate a safe evac.
I would not like to do it on a burning 747 with 300+ unprepared men, women, children, old folks and drunks!
Have you ever seen the video of the 1970s Pan Am San Francisco accident? Emergency landing, out of trim CofG and strong winds. some slides failed to inflate fully, others blew away in the wind and as the aeroplane tipped onto it's tail, the front slides became vertical and injured a number of people. Again, they had time to plan and had a small pax load.
Hope this is useful.