Whatever it is, it's f/2.0 or faster across the board and has IS & a sweet bokeh. If it's a zoom, I really don't need more than a 2x zoom range (unless it's a "standard" zoom trying to do wide & tele, but now we're dreaming). Short/fat is preferable to long/skinny.
Also, I very much like the idea of the integrated switchable 1.4x teleconverter as an alternative to mega-range variable-aperture zooms (I'm looking at you, 100-400L). The big lump on the side is less cool, but it beats schlepping a TC on & off by a long shot.