wgetting a big file uses 75% cpu (according to osso-statusbar-cpu), I suppose (but I may be wrong) that a sizeable part of it is due to the wifi transfer (on another arm system wget takes just 30%).
I also suppose (but again, I might be wrong) that cpu consumption translates to power consumption.
Btw, I don't really care about wget performance, I noticed the problem because it's very taxing to stream video to the tablet, in part due to missing video optimization (even with the great work done with the mplayer port) but in part due to the wifi (lack of) performance/efficiency.