At my dps, ~83k on WD, my reaction after a bit of Act I/II/III farming on monster levels 3-5 tells me, ML 3-4 is going to be the sweet spot for now. Even at lvl 5, felt the difference in kill time extending to a point where the extra magic find won't balance it. That said, at lvls 3 to 4, still felt very close, good extra magic find as a bonus at roughly same kill speed as 1.0.4.
To net it out, bonus magic find just for hitting patch and the ability to farm Acts I and II in addition to Act III. Act IV due to size is probably still not efficient / viable. Extra bonus of Infernal Machine stuff -- only have 1 key so far from Act III (had maybe 2 or 3 stacks of Valor when I got it). Also came across Act II warden by no drop.