Hi guys, if i can offer my tu'pence worth on the subject (having worked 4years as an aerodynamicist on the A380),.........
Kruger flaps are a cheap option (more or less a flat plate with hinges, but aerodynamically not the best solution). They are relatively predictable (as in they will stall at a given alpha, that will change very little with conditions),.......
With regards the big-bus, we were unable to install Krugers on the inboard section due to the high camber (curves), and the complexity this added to the design (unable to locate the hinges basically)
Further outboard, a Kruger becomes less beneficial. The loss of lift between a Kruger and a Slat is high on the outboard sections, and is manageable on the inboard. Added to this, there are complications with regards to locating the actuation devices within a relatively thin section of wing, which may add weight, rather than save weight (which would be the reason of trying to bring Krugers into the design anyway!!)
Hope this adds confusion!!!
FP