I can imagine! Personally I love ADs - smooth sailing for both parties involved, but you know, certain watches you cannot purchase new. I'm mostly after limited eds. I have made purchases through WUS without issue, but those were under 1k, and you do get a good sense of the person based on their previous post history and the way they communicate via PM.
For more expensive pieces, I would much rather work with a broker, is there one? I would tell them what I'm seeking, they find the watch and negotiate with the seller. That's how I purchase my cars. I don't sign the papers until all the hard work has been put in by someone else, and they get their flat rate in compensation. I would gladly pay for these sorts of services.
The only drawback - you don't form some potentially good connections with like-minded collectors, or dealers.