Ranging from games to interactive maps, some of these apps are actually useful and give a certain extra value to your phone. I admit I've been fully hooked by a few apps myself, as they tend to make my life easier.
Hilton has realized the potential of mobile apps to a certain level, as they already have an app of their own.
Developing this add would probably mean taking the app worldwide - not completely sure if it works in every place of the world yet, or in every hotel.
However, SOME areal Hiltons have also developed their own, local apps. A quick search through iTunes' Store reveals that one of these is A Hawaiian Hilton resort's iPad app.