For me, this is a do-or-die feature. I use Today, Upcoming, and Later on the web version to prioritize my tasks. Then, I rarely look anywhere else but Today, Inbox, and New. Not being able to prioritize tasks in the iOS app is frustrating, to say the least.
I usually clear out my Today tasks any given day, so in iOS, the Today group doesn't even display; so, I can't even drag tasks into Today! The way it works on the web app is ideal. Please, Asana team, build this into the iOS app!