If you primarily stay at ES, I don't think you'll see a big difference between gold and diamond. ES rooms are for the most part identical, therefore, an upgrade might take the form of a corner room or a room with an additional once in a great while. I opt for additional points on my profile, so I don't get the free snack with bottled water in the room as a diamond. That being said, every so often the hotle will give me my extra points and leave me a free snack (nice touch).

Depending on the front desk personell, you might get a warmer "hello" or a special favor from time to time due to your status, but not a huge difference (in my opinion). That being said, if one night will move you to into diamomd go ahead and do it...it wouldn't hurt to have the status. Can you spend less and make a mattress run at a less expensive Hampton Inn nearby?

Regarding full service Hilton properties, you will notice the diamond benefits a little more frequently - i/e. upgrade to executive floor, etc. Again, for the cost of one night I'd go for the diamond, but don't expect the heavens to open up or trumpets to sound when you make diamond. It may be a let down for you.