If you are staying in full-service Hiltons, you should get lounge access. Not all of them have it, but that's a big plus for me. I get the best treatment as a Diamond in Asia, followed by Europe, and better in the higher class hotels (e.g. Conrads) than the normal business hotels. In typical US business hotels, my experience is that Diamond is better than not Diamond but it only occasionally leads to a suite upgrade.