I have Ride Hopper and used it whilst in the park on the Memorial Day week - a time with high press & VP activity, soft and tactical openings of Star Stours II, as well as The Little Mermaid. Needless to say to parks were somewhat crowded and confusion was high what with all the cordoned off line areas.
For the most part, the times were very close for the not-new, popular attractions. You could tell if they were not close by the length of time since last update. We discounted times with more than 30 minutes since last update. That is except for the less popular attractions. Those had an ebb and flow that followed within the normal variances for the day. Only when we noticed a new update for an attraction we like with a very low wait time (within a reasonable distance of our current location) did we change plans and go there.
Over all - Ride Hopper works well when people post their times (which we did quite frequently), but less well when there are not a lot of people posting updated wait times.
I am waiting for the version that uses your GPS location to automatically calculate wait times based on proximity to attraction entrances and loading areas. Then the wait times can be more accurate since you won't have to manually enter your times - if you remember to do so...