Trouble is...how do you really know how thorough they are unless you actually witness the procedure and indeed, you actually know what they should be looking for. I guess, It all comes down to trust but everyone should bear in mind that dealer servicing has to be done at a price acceptable to the customer and produce a reasonable profit.
I am sure there are plenty of good guys out there but those of us who are able to do our own, sleep far better at night!