I'm also very interested in this lens.
One of my most used lenses is the FA 50 macro together with the 31 limited. Somehow I hoped for a f/2 instead of a f/2,8 (now that would have been very interesting!), but I guess somehow that's impossible to achieve in a macro lens of this focal length. Anyway, if this lens is up to its' specification, I won't hesitate and buy at whatever cost.
Now I see the European price will be €400,- and that sounds ridiculously cheap to me. It's like hitting the jackpot... Hope it is as good as that other hidden Pentax secret: the FA 50 macro... Holding my breath.