$2500/nt.? LOL - nobody's at that level that I know of, provided you redeem the "logical" awards in each program.

For kicks, I ran my own numbers using my own status levels. MR Plat, HH Gold, SPG Gold. I considered a high-quality mainline hotel for the logical stay length in each program (5 nights in MR and SPG, 6 nights in HH). I assume the correct credit card is used for each stay.

For this purpose, I did not attempt to count my favorite award - the MR Travel Package - because there is no good parallel in HH.

I did not factor in promotions because they come in so many forms. For example, Marriott does lame points promos but better gift card discounts, bonus bucks, and Elite Exclusive Offers 2-for-1 nights. It's hard to quantify them in terms of points.

I used Marriott Cat 6, "new" HH Cat 7, Starwood Cat 5. This is somewhat subjective, but it fits with what I tend to book in reality. I have yet to book SPG Cat 6/7, Waldorf, or Ritz using points.

Anyway, my numbers...yours will undoubtedly vary.

MR - Cost is 120k points for 5 nights. Earning is 20 pts/$. $1,200 spent = 1 night.

SPG - Cost is 48k points for 5 nights. Earning is 5 pts/$. $1,920 spent = 1 night.

Today's HH - Cost is 175k points for 6 nights. Earning is 23.5 pts/$. $1,241 spent = 1 night. (I use 23.5 because "today's" HH points were banked primarily with a credit card yielding only 6 points per dollar.)

2010 HH - Cost is 225k points for 6 nights. Earning is 29 pts/$. $1,293 spent = 1 night. (I'm giving HH some credit here - they've given me a path to Diamond and added 3 extra pts/$ on the credit card.)

2010 HH without the Surpass card upgrade, remaining at Gold status, would be $1,595 spent per night.

There are a couple reasons I think SPG appears to be on the high end:

(1) Their "no capacity controls" feels more real to me than either Marriott's or Hilton's. I can't prove it, but when I look at high-demand situations I almost always end up booking a SPG award because MR and HH have no awards available - even if all three brands are still selling rooms for cash.
(2) I think SPG realizes that most of its frequent guests are reaping a lot of benefit from general credit card spending. They can keep their hotel-spend requirements higher and guests are still happy because the CC is so powerful.
(3) SPG is geared to reward the Plat member more than anything, with better Plat-only promotions and a meaningful-value Plat stay bonus. Marriott and HH both offer "welcome amenity" points if we choose, but the amount is small and we usually opt for something else.

Anyway, my conclusion here is that a current HH Gold can mitigate most of the devaluation by going "all in" with Hilton. Someone sitting on the periphery - using the CC a bit, doing a few stays, remaining Gold - gets hit hard. Marriott becomes the more rewarding choice - even if you only do Gold-type business with them.

Somehow I don't think this devaluation is going to incentivize a bunch of people to go chasing Diamond. I think it's going to drive people to other programs.