I love the UG! I use it mainly for "research' before my trip. I do bring it in my suitcase, but it stays in the hotel room (I don't carry with me in the parks). Has tons of great information, including reviews of restaurants, hotels, and attractions, etc.
I have never been a Passporter user because I don't carry a guidebook with me in the parks (one less thing to weigh me down!). I know folks like it for the maps, the compartments to hold your receipts, things like that. But since I don't carry a guidebook with me at the parks, its cool features are wasted on me.