YAPP features an easy and intuitive user interface for creating a professional-looking mobile app which has TONS of functionality. I have been using the service for years, and have built multiple conference apps with it, all for public education, curriculum, instruction and leadership. If you look around at conferences, just about everyone will have their faces buried in their phones, tablets or laptops. You might as well capture their "digital attention" with your content. I love the YAPP message boards, picture walls, Twitter feeds, and, as an event organizer, the ability to set up session information and schedules. If your users log into the system, they can also build customized itineraries of breakout sessions to attend as well as their locations, streamlining end-user access to your conference sessions.
On the back end, the customer service with YAPP is amazing. they have always had my back if I need their help. Sure, the platform subscription is expensive up front, but that plan will service most organizations that don't have the resources to custom-sourced their own mobile app from the ground up. Further, you can build UNLIMITED apps with an unlimited user pool.
Entering the conference session data can be tedious, and there is really no way around this. However, if you use a spreadsheet to build your initial conference schedule layout, session description, location, and other pertinent data-- you can then use that spreadsheet to import your sessions with direct mapping. This saves you a big step when it comes to conference design, but it only works if you begin with the end product in mind and make that spreadsheet from the origins of the conference planning stages.