I don't think it's as disastorous as everyone seems to think because remember a Lambretta chain runs in the opposite direction to a motorcycle chain. If it ran the same way as a motorcycle chain i think it would spell impending doom!
In the first pic the chain looks completely shagged, i must say!
However i think it's too close to the rear sprocket and it doesn't look fantastic quality in my opinion. I think that any chain guide with springs and other components that could possibly fail and drop bits into the engine is not my cup of tea. I'd prefer to stick with a fixed nylon style.
Why is the back-plate height adjustable through a plain slot? Any loss of grip and the whole thing bounces up and down on the chain till it fails....?
The chain edges will cut into the nylon and in short time that split pin will be ragging on the slipper.
The 'kink' in the chain from slipper to crown wheel has to agravate wear on the chain rollers.
Concerns about the spring (looks like a clutch spring). I hope the spring has a seat machined into the nylon slider and that it is deep enough. Imagine as the slipper wears down the angle of the spring base to the slipper will encourage the spring to bow (to the rear of the engine). The spring will be encouraged to pop-out more and more as wear increases, tension decreases and the chain flexes more. Outright spring failure will be more lightly the further it goes. Coil springs are supposed to flex in one axis, only!
Concerns about the pivot: the first one seemed to have a counter-sunk allen cap bolt securing the pivoting piece, the second one a (hopefully shouldered and not threaded!) stud and nut arrangement. Why?
Why is the full underside of the slipper curved? Some design concept failure?