Which is most important for a service centre, the reception, the the quality of repair or the repair time?

All three equally important.
You can't compromise with any of those.

The main thing is quality of repair and repair time

All these three points are highly essential for a service center. The costumer's time is very precious, and we must keep it in our mind. And the quality of repair is the key to make a good relation with our customers. Quality plays the key role in trust building.

All of them, if we want our new costumers as regular ones...
The time, when costumers had been searching for services is past.
Now, we have to find the way not only to attract our new costumers, but to keep old ones too.
So, if we want to "survive", surrounded by merciless concurrence, we have to take care about everything.

All of them are among main tasks in a customer service center.
they complete the customer service altogether and any weakness in one of them affect the other parts and all of the customer service process.

The reception

The most important thing for a service center is the quality of repair as its what the customer came for in the first place then the repair time which revels how good are the people working in the center then the reception as there main work is to Delivery and receipt the devices