It took me a while to actually get to properly start using parktronic and i must admit i struggled somewhat. I think the following is useful to bear in mind:
a. For parallel parking, i have to drive a few metres past the parking spot before i get the notification that it has detected a parking spot. This is much further along than i would go if i was manually parking the vehicle myself. That said, the vehicle does a great job of actually parking.
b. I usually park on the passenger side of the road so i dont think i need to indicate, however, if you are planning on parking on the driver side of the road, then you need to indicate (right indicator in the UK and left in europe and US i presume). As a general rule of thumb because of point a above, i always indicate while it is looking for a spot just to warn any vehicles in the vicinity about my intentions.
c. In autumn especially when there are leaves on the road covering the kerb it sometimes can mount the curb but this is understandable.
d. The car usually leaves a generous space from the kerb of around 5 to 6 inches and i live on a narrow road in the UK and therefore tweak the parking after manually. i've got no issues at all with this.
e. The car will accelerate and brake itself, though, i usually lightly brake while it is performing the maneuver as it does it really swiftly and turns into the spot very close to the car ahead ! The first time i used it, i forgot that i need to keep my foot on the brake before changing gear (the car was stationary as it braked itself) and i couldnt engage drive (rookie error ofcourse as i normally drive manual transmission cars prior to this one and had no idea what i was doing).
f. Just in case, engage parking break after it has parked though i think it may do this automatically?
g. let it steer and keep your hands clear of the steering wheel as otherwise it will cancel the park assist mid flow! this happened once when i had just got the car and wasnt sure at all about its dimensions! So i had to drive off and find another spot.
In summary, it is a great feature and i love it. It may take a while to get used to it, but it's a favourite feature. Clearly S and E class mercs have full remote parking vs basic A class parktronic but it is still really good in its stripped down A class entry level form.