The Zendesk Sell mobile app's syncing with real in time usage is a huge issue. The activity feed does not sync with actual usage (it does not matter if the app is refreshed).

Searching within the app is pretty much useless due to the lack of robustness of the app. I've directed our team to use Smart Lists (set up on the desktop) and search within those because a general search never works. 

The main use for the app for our team is the mobile map. If the desktop also had a map for contacts/leads it would be helpful.