Canarsie, some brief thoughts:

1. Miles are still a valuable proposition. They just aren't for retirement. Earn and then burn, that way the two are aligned and there isn't a devaluation of miles earned in one period when you attempt to redeem under a new award chart with higher prices.

2. In some ways, they're getting more valuable than ever. Alliances mean greater redemption opportunities. I remember even at the beginning of alliances if I wanted to fly Air New Zealand on a transpac in F United would only fly me in coach to NZ's gateway. I love redeeming AA miles for an award on both TN and QF, and redeeming US miles for an award on both NH and TG (both of which I've done recently).

3. But of course there are challenges. There rae no guarantees with frequent flyer programs. Benefits can and will change at will. The prices of awards will go up. These are very real currencies, but with no independent central bank to keep inflation in check. Hence #1 above, earn and burn in the same period.

4. Not all programs are created equal. Delta is legions behind both AA and UA in my opinion, at least as a general proposition. Now, if you need to spend most of your time on DL metal (in 2-class equipment, anyway) then it makes sense to be with Delta. But their international upgrade policies and sky-high award chart make them generally unattractive, at least to me. Then there are pretty good regional programs like AS... and if all you care about is domestic upgrades, by all means check out NW (or AA if you can become an EXP).

5. Diversification is key. Redeeming on a single carrier or from a single program can be difficult, especially with very full planes. It makes sense to rack up miles in a single program until you have enough to make them useful, but then it pays to diversity. It's wonderful to look for an award and be able to choose to use miles with UA, DL, AA, etc. Building up miles in an account with each alliance can be very helpful.

6. Don't forget hotel programs. Love Starwood's redemption properties, even if I don't like how expensive some of the best properties have become. The Starwood Amex is my choice for credit card accrual. Plus the flexibility to transfer points to so many programs is great -- optionality is key.