Counter staff have absolutely no way to tell what type of Visa/MC you have unless they have the card themselves or ask the customer.
...they don't know (or care) about the colour of the plastic or the text/logos on it. What matters is what they find out after they swipe the card - and get presented with the option to surcharge your 'premium' card.
Platinum sounds good with the higher level of purchase protection and travel insurance but who would use credit card travel insurance exclusively.
I do. To tell you the truth, I've been travelling abroad for much of my life (mostly biz) and if I had bothered to have travel insurance I would be much poorer than I am now. Fact is that most travel is uneventful and does not involve enduring a 'claimable' event.
That said, claims on Citi's credit card insurance (run by Zurich I think) work well. I've had a couple of minor claims - lost a pair of as-new, expensive sunglasses about 3 years ago and a mid-priced digital camera last year, both less than 3 months old. The claims were both processed smoothly and I received the money within a few weeks. Technically (according to the policy) I was required to furnish police reports, which I did not have - the losses occurred in 3rd world countries where police are either hard to find or corrupt. Zurich, however, did not even ask me for these. I guess the trip wire is there though and probably used if the claim is more substantial or you establish a track record of making frequent claims.
I would never separately insure for the loss of personal effects - that's just too expensive compared with the value of claims that I would likely make over the long term. However, if the cover is complimentary, of course I'll claim!
I have also heard of a couple of people who had medical-related claims via the Citi Platinum. Their claims were smoothly handled.
As always with this stuff, it's wise to read the policy and in particular the exclusions. If you realise that it doesn't cover your situation adequately, then get supplementary insurance elsewhere.
The important point is that Zurich, on behalf of Citi, seems to run a smooth claims operation.