I think you'd need to compare the benefits of Diners vs. Amex based on where you go and what you do. For me, Amex has provided better service and benefits that more closely align to my travel needs. YMMV.

I liked the idea of the Diners Club exclusive lounges....until I noticed that the only one in the US is in Miami, where I never go.

I will have to do more research into AMEX cards to understand more about how they work. Opening three credit cards at the same time is a big step for me!

To underscore what others have said, if I were you, I'd go with United and SPG Amex!

I didn't see it mentioned yet, but have you considered the Citi PremierPass Elite card? If you use it to book your flights, you get points for the miles you fly. Those points, when matched with spending, become Thank You points. So if you buy tickets for a 10,000 mile flight, and spend $10k on your card, you have 20k TYP which can be redeemed for a domestic flight worth up to $400 that you will in turn earn miles on. For some business/first class awards you can get up to $0.03 per point value.

I won't bore you with the details in case you already know about it, but I would consider it and check out the credit card forums for details on the fixed price awards you can get with TYP.

Whoa, really? Is that true with every airline? I get points on miles flown as well as the cost of the ticket? Is that true both ways? (so on a 500 mile r/t flight, 500 TYP going, 500 returning) That's great for international travel. Is it a 1:1 ratio of TYP to miles on every airline? Does it transfer to FF miles, or just tickets that they issue?

To make sure I get this straight, Using United Visa (if I'm a United FF member), if I spend 300 on a ticket from Chicago to NYC (800 miles), I get a total of 2200 miles - 600 from the ticket, and 1600 from the flight itself.

With this Citipass, I would get 1900 TY points (300 from the ticket, 1600 for the miles flown) + 1600 for the flight, right?

That would definitely be worth it IF I could redeem it for miles. If it can only be redeemed for tickets, it would be less worthwhile because I would essentially be building two parallel FF accounts that can't be combined.

You didn't get it right. Not quite. The key words are "when matched with spending."

As edlin303 had pointed out, there are a lot of discussion on Citi Thank You Points. You should visit the Other Credit Card Programs Forum to check it out. MileBuzz! Forum is not the right place for those extensive discussion threads.

Here are two sample threads for your viewing pleasure. (Yes, you have to do the homework youself. )

Citi Thank You Points Devaluation

Citi Thank You Rewards/Airline Redemption

OK, so I think I get it. If I buy a $300 ticket for a flight that's 800 miles each way, I would have to spend an additional $1300 on my card to get a full 3200 TY points. Is that correct? So that's about a 2:1 ratio (assuming spending thresholds are met) + regular FF miles, although the miles are not going to be as valuable if you're redeeming on any airline that comes closest to the spending cap because you're going to be spreading your miles all over the place, right? it sounds almost like you're giving up on accumulating the regular FF miles and focusing exclusively on TY points awards. If that's the case, then it's similar to any other 2:1 program and still inferior to the hotel rewards programs, no?

IMHO thank you network is most valuable to those who maintain status on a number of airlines, because you can earn miles on the thank you network flight award tickets.

Flying twice per week and saying in 5 hotels per week (with two different visits) will net you a TON of hotel and airline points. Why on earth would you want a credit card that gave you more?

Get yourself the best cash back card you can find. You're likely spending $100k per year on travel by the sounds of it. Some credit card programs will pay you 3% for the top spending categories. This would include things like hotels, airfare and meals.

Why not end the year with SPG Diamond status with enough miles for a stay at a very nice property, a ton of CO miles to use on a SkyTeam flight somewhere nice and $3k in spending money?

It's not a bad idea to go with the cash back, but I found out a couple of weeks ago, I get reimbursed for the cash value of rooms even if I use points to pay for it. That's the coolest fringe benefit ever! So if I get 6 days of free hotel stays, that's as much as $1800 in cash just for giving it up. That definitely beats the cash value of the points itself.