Regardless of the existence of an ?ajax engine? I think that the approach is quite good. Maybe adaptive path is trying to bring a ?ajax engine? to market.
Jason Fried wrote on 37signals:
As with anything, it?s not the technology that matters, it?s the proper application and the execution of that technology that counts. And most of all it?s how well we hide the technology. I?m very excited to see what comes out of this new movement. I?m looking forward to some stellar new web apps using Ajax and derivative tech combos.?