I have tried two Surface Pro i5 8GB tablets over the past two weeks before finally asking for a refund with Amazon. First one showed signs of overheating and had some screen damage. The replacement did not run much cooler, built up a static charge when connected, and (also) drained in about 4 hours normal use.
Battery life is terrible, even after trying every tweak described in the various MS Answers topics. Just this morning I saw my tablet drain from 100 to 80% in a half hour Skype call. No way will you achieve 10 hours under normal working conditions. For me that was the final straw...