Oh dear, the new tech preview still doesn't have an option for rotating with the z axis locked! The viewing functionality is pointless for AEC without having a locked Z axis (either lcoked by default or a dedicated navigation tool with z axis lock, such as in Autodesk Design Review). Imagine a client trying to navigate around a building... no chance! You'd be better off removing DWFx viewing. Having siad that, it is usable on the iPad, just not desktop.
I first raised this around 18 months ago during a 1:1 feedback session on Autodesk 360 at AU 2012. But all this time later and no change. No wonder I feel my feed back is falling on deaf ears...