We have been using it for the past couple of weeks. We have the 9.99 a month data plan. It is 25 megs/month; we've used 7.5 megs and that includes occasional emails, facebook and so on.
The fast pass return times have been 100% spot on, down to the minute. The attraction wait times have been 100% accurate with what is posted on the attraction.
The restaurant part hasn't been used much by us, because we know that, but we did use it once out of curiosity. It clicks you to a link that dials of disney dining where we made a reservation. Maybe now that disney.com has all the menus of the restaurants on line they will put those on it also.
The daily information like park hours and show times are handy to have. It shows you the next show time rather than all the show times which is a bit of a drawback.
The characters. OK. It didn't know anything about the star wars characters the last few weekends. Fine. But it didn't even the fact that Mickey-Donald-Goofy-Minnie were there. In fact, it told us that Donald wasn't there even though we'd seen him not only at the star wars line but earlier that day (um, I guess he ran back and changed his outfit) at the animation building. If you were a typical tourist and you had a kid who wanted to see Donald wouldn't you want to know that he is right over there in a storm trooper suit? Also at the studios, there has been several times that there were extra characters at the animation building that it didn't know about. Also, one day it said some characters were at the BAH when they were inside the animation building. One day we also saw pooh, tigger, rafiki, wendell, and liverlips at DAK at the GTGS and it didn't know about those. Basically, for characters it doesn't seem to get much more information that what is printed on the paper guides, which is disappointing, because the whole point of the thing is that it should have up to date information that could be updated on the fly. If I wanted a piece of paper I can pick one of those up, you know? Another little example, one day at MK it said Lady Tremaine was at fantasyland gardens when she was actually up by where pooh's playground used to be.
My wife isn't a big fan of it at this point, I kind of like it. Also, some of the trivia questions are incorrect. I think it is worth the 10$, wish it wasn't such a closed system.
Here are some examples of characters it didn't list as present: