In reply to Erstwhile:
Thanks all for the replies.
Re concerns over gear failure: I'm not so much worried about my gear failing (though it has happened with catastrophic consequences), as I am about my body failing when taking a high impact force on a face with several steel protrusions.
I don't think I agree with concerns this gear is specialised: I think that's an advantage, and a necessity. You want different gear for via ferrata than you do for climbing (much higher impact forces for one). This specialised gear to prevent a VF fall would be in addition to your usual gear.
With the Aa bloc, I agree clipping in a third thing (in addition to the two via ferrata carabiners) would be a bit of a pain. But the avoiding a large fall seems like a great reward for the effort. Perhaps to be used when climbing on rock without using the cable, or if climbing a section where you think you might fall.
There's a new skylotec due to be released this summer, the rider 3 (looks pretty similar to the skyrider 1 and 2).