I was advised by a Cessna rep recently that Cessna will not be backing the old Lancair 400 electric de-ice system. They don't think it is proven enough to be associated with the "Cessna" name, and there are anecdotal reports of weird problems with it, melting bits of wings or elevators. The reports are countered by more anecdotal reports of the problems having been caused by dealers mis-wiring the heating elements...
I think a major factor for performance degradation through icing is loss of prop efficiency. I have a TKS de-iced prop which works brilliantly; with some 10mm of rough ice on the wings I lose 5-10kt but the prop is spotless clean.
The prop-only TKS system is quite cheap (1/10 of the full system and hardly any weight penalty) but is not certified for anything whatever, and when the plane was delivered new, the CAA inspector insisted on an INOP sticker being stuck over the ON/OFF switch
. That was after he required EXIT stickers on the doors
which in turn was after he demanded that the IFR GPS has the IFR features disabled, even though the DGAC type certificate covers BRNAV and the plane was delivered with "approved for enroute IFR" factory stickers
But having seen how well is keeps the prop and the front window clean, I think a lot of people blame wings etc for loss of perf when actually they are getting some prop icing which is robbing them of thrust.