Unlike the previous forced completion, Dennou Coil did not envoke any strong emotions. It was okay. The disappointment originated in its original manifestation of intent: they promised a lot and fell short.
Animation quality was oddly poor in many places. It almost feels like they did it on purpose, aiming for a minimalist expressiveness, but failed. If we look at, say, Windy Tales, the art is even sketchier in there, yet it's miles ahead in the artistry department.
The plot and the final explanation made sense, except I would prefer it unrolled more gradually instead of an Agata Christie style infodump in the last chapter. Still, better than Lain.
P.S. I liked the epilogue with its changed color key.
P.P.P.S. I still think that the filler is inexcusable in a show like this.