I have a pumped 61 SF and like it very much. I bought it used 3 years ago and never missed a beat. The only disadvantage I see over my previous 61 FX is that the FX "warns" you when the tank is near empty and the SF pump just shut instantly. I crashed my plane because of this (maybe it was me insisting torque rolling low for too long).

Just my opinion here but I think newer OS are of less quality than these older SF series.

I did not notice any difference in fuel economy. I was thinking of it because the carburetor is much bigger than standard (more air means more gas).

It starts really well. I choke it very much and with only fingers on spinner, a small clockwise flip just before compression and it always start first or second flip if choked properly.

Hope this helps.