If you don't already have the Marriott Visa, then there's no question about it: Platinum is worth it. Even without the Platinum hook, the new Visa more than pays for itself. That's a no-lose proposition.

If the question were "I already have my 15 Marriott nights and need 10-15 more EQN's that I have to pay for out-of-pocket to reach Plat. Should I do it?" I'd say, for most situations, no. The outlay of several hundred dollars or more for the sole purpose of reaching Platinum generally won't be worth it.

But yeah, anybody who stays at Marriott at all - and lives in a market with access to the "new" version of the Marriott Visa (with the annual free night cert and the 15 EQN's per year) should be carrying it regardless of whatever else they have in their wallet.