of a positive experience...
However, you say, "one of the faults, the socket, proved to still be faulty" I infer, from what you have said, that this was one of the faults it went in for.
Apologies if I've misunderstood, but sending in a faulty unit, being without it for 4 weeks, (or any length of time in fact), and having it returned with the same fault, seems to me not to be the kind of thing that merits the description "exceptional service", (assuming the adjective "exceptional" is supposed to be a positive thing!)
I appreciate you've explained that it might have be a recurrence of something repaired, but even so...
I am of the opinion that even if the service had not, to use your words, "been a little slow", and been returned, with no faults, after 3 weeks, it wouldn't qualify for the description "exceptional service". As the eventual outcome was a repaired unit that you are satified with, I would suggest that "Satisfactory" or "Adequate" would be more appropriate adjectives.
I don't mean to start a row!