Regarding custom event apps, I suggest organizers make them as basic and robust as possible. An attendee only needs a handful of useful information (agenda, speaker/attendee profiles/address, etc) that’s reliable and fast to browse plus a way to find/contact/schedule-a-meeting with other participants.

I see too many mobile apps loaded with fancy features that no one will ever use and that make it heavy, slow, buggy, expensive (to develop), etc…

A typical example is adding a backchannel: people that use Twitter already have a favorite app and that’s the one they use to tweet, so why duplicate that function in your custom event app? Just let them know what the hashtag is for the event and they will use whatever they prefer to take part in it.

Another suggestion for those building a custom app is to add Sponsor logos (and offers/goodies, meeting scheduling, etc) somewhere prominent on the app (keeping it functional) so that you have an extra item to propose to a sponsor, which btw can cover the app’s development costs.