Should repaired equipment be stated in the ad??

Well said Chadnliz .

Like I pointed out above, there is not necessarily a negative stigma attached to service history. Vintage equipment needs caps replaced, tuners need re-alignment, old tube gear often requires cleaning of oxidation and can benefit from new wire.
Do you consider these to be repairs or maintenance? And what about mods? I see many ads crowing about mods having been done.
If it was factory R&R what is the problem? Items that didn't get caught by QC the first time through are returned to the factory for individual attention upon failure. These, I suspect, leave the factory better than new having received individual scrutiny.

Why so anal everybody? I buy used stuff aware that it is as likely to fail as new gear. The difference is that I bought it for hundreds or even thousands less than the original price. That leaves a lot of room for repair dollars in the unlikely event that they are needed.

Another point I might make is that most sellers on this site are overly concerned about their reputation and will bend over backwards to accommodate an unhappy buyer. As in any other area of transaction, you will find a degree of risk, but it seems that many of you are over-reacting to a problem you haven't even experienced.

Remember that you are doing this for fun. You have enough other things to worry about, don't you?

If it's repaired, there's nothing broken. What is there to report?

I generally agree with this. I think it's expecting a lot to have a policy of disclosure in the ad (and it's unrealistic to expect it to be followed). That said I think a request for service history (ie during negotiations) should be responded to completely and honestly. If you think it's not full/honest disclosure walk away (btw, A'gon DOES have a policy on this). Your description of the terse response you received is familiar to me - when I think someone is not answering the question asked I walk, unless I decide I'm willing to take a risk on a deal too compelling to pass on.

I agree with Macrojack in that most people on this forum are overly picking about equipment purchased here. It is "used" which means just that! You can't expect it to be like new. Unfortunately, some folks just don't get that.
As was stated when you buy something used, you're usually getting it 40% off of retail. If you want all this piece of mind and guarantees, then buy it new!! When you buy used you're taking a chance, bottom line.
My rule of thumb is manufacturer reputation and service record.(example: audio research equipment is known to be built like a tank and has a very good service reputation) I ask for serial number and then contact the manufacturer to see if the piece has ever been in for servicing. That's all you can do and even that is not 100% foolproof because if the piece was repaired by someone other than the manufacturer, you still want know, unless the person divulges it. If they don't, then that's the chance you take.

I would feel the same about a car.