Don't forget lithium ion batteries require periodic recalibration. MS recommends running your battery all the way down once a month and then a full charge to accomplish this.
Hmm maybe ill try that.. only problem is last time I tried it the surface shut it self down before it fully discharged.. :S after its self shut down it won't turn back on unless I plugged it in.
And recycling all those old batteries thus the U.S. electronic recycle laws...there is real money to be made through hicap battery design.