I used to Supersize here and there, but I don't do it anymore. I feel that miles have been devalued lately, and I don't think it's really worth it anymore.

ETA: Oh and btw, be careful if you have nested itineraries; Supersize goes crazy. (E.g. I'd have a long business trip from A to B and I'd have several other flights B-C-B, B-D-B, etc and Supersize doesn't like that. I TTUed and got my miles, but just so you know it's a hassle if you have more complicated itins.)