@Gavin *********
I've also never had a problem, but what I'm happy to try and avoid is the before dawn travel to Cheang Wattana to then queue for an hour or so before the doors open, scramble for a ticket and then wait further for my number to be called.
If I can just book a convenient time, only need to get there 15 minutes before my appointment, be seen almost immediately and then done, why not?
It's a free system, I've only read about it up until now, so this will be my first time of trying the system.
In theory it's progress, why not give it a go?