Not to pull off topic, but I have a World MC, which also provides concierge service.

I can't compare directly to the other two, but my experiences with the MC service has been more along the lines of what people are getting with the Visa. Any time I have called, service has been prompts and helpful. More importantly, they have been significantly faster than I would have been doing the legwork myself - and this is including time to dial/connect/verify/etc.

I have been looking at dropping my MC and the wife's DL AmEx for the AmEx Plat, with the concierge and the domestic companion being the two great draws, and going through these threads, I'm starting to wonder if it would even be worth it.