Don't let the hate get to you. I'm not sure what the wattage is on a 5750, but on a 5770 it's about 2:1 mh/j. They're small but stout.
Actual power consumption might differ some but the TDP for the 5750 is just 86 W compared to 108 W on a 5770.
And as for efficiency, I can say that after some comparative testing done by adding and removing my 5750 into my part time mining rig next to my 6850 I got a total system wattage increase of ~108 W (at the wall).I'm not sure how much of that is due to the extra CPU cycles but if I assume negligeable increased CPU power consumption and factor in my power supply's (in)efficiency, my 5750 is using up ~86 W.
That's 86 W while overclocked to 955 MHz and pumping out a nice 200 MH/s. 2.3 MH/J is not exactly garbage in my book.