This lens's DC autofocus mechanism is impressively fast - it has certainly taken Pentax to the next level, much closer to the industry leaders (Canon and Nikon). We hope that this lens sets a precedent, and that future Pentax lenses will boast the same improved technology that we've witnessed in this lens. Due to its quiet performance and lack of a distance scale, the only true way for you to experience this lens is to try it for yourself! Simply put, the new autofocus has us very impressed!
The other great thing about this lens is that it has relatively high magnification and a relatively low minimum focusing distance, meaning that things will rarely be too close to focus on! The maximum magnification can be achieved when the lens is at 135mm.
At CP+ 2012, Pentax told us that the DC technology used in this lens is targeted at the intro-level market. Why it's still not clear why this seemingly-superior system isn't slated for use in pro-grade lenses, Pentax hasn't release any lenses with built-in focus motors since the 18-135mm (as of mid-2012), so we can't draw any conclusions quite yet.