Just out of interest, I thought I'd run a quick poll. Obviously, this doesn't include those not yet out, but I thought I'd do a quick survey of the main PDFs available.
I have my own (Four-Color to Fantasy), plus volunteer copies of DNW and Vigilance, loaned by their respective creators. I have yet to read them, though. Sorry.
As of right now...not any of them. I am still biding my time, circling.
I think i will be definitely getting Mutants & Masterminds in October (if that IS the real release date!!!).
I am also looking at 4CtF as well.
I have Deed Not Words and its supplement Laying the Smackdown. My only problem with them is that I wish they were Hard/Soft cover books. PDF printing is killing me!
I am also looking at 4CtF merely because of its tool kit approach otherwise I simply have no interest in any other Super Hero games. DNW does it right and does it best!
My favorite has to be 4CtF. The way it integrates with standard D20 without needing any "special" rules was the selling point for me. The only thing that it needs are some more powers and superfeats, but that is being worked on from what I understand. I am thinking about opening up a section on my website for renditions of famous comic characters and such.