Almost every driller there is very good to excellent to great, but they are human beings. They are under a lot pf pressure as thousands of people will be asking them questions; some people will get on their nerves. Try to catch them at good times (they can get VERY, VERY busy) when they have the time to take care of you properly. Be courteous, ask questions nicely and respectfully and you'll probably walk away VERY happy.
Reminder: they won't be there to drill a ball when you go home, so take your drilling sheets (specifications) with you and try to write down notes very soon after talking to them. You won't remember it all an hour or two later.
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"...for advice is a dangerous gift, even from the wise to the wise...."
J. R. R. Tolkien