I purchased a SP7 i7 16GB a week ago and have been very disappointed with battery life and performance. I would say I've also only been able to get 4-5 hours off a charge browsing online/youtube videos etc., nevermind anything more intensive for work. I downloaded/installed all updates, ran on "battery saver" setting, changed windows visuals to "best performance", pared start-up applications down to 2, turned off background programs and any Cortana related settings and also tweaked the advanced power settings to no avail. It also felt more sluggish working in Lightroom 6 compared to my 4 year old i7-6700 desktop...the SSD in the surface pro is noticeably slower. When plugged in and bumping up to "best performance" the fan was far more noisy than on my 7 year old Asus K55 laptop, which I was hoping to replace. I'm leaning towards returning the Surface Pro after reading many other comments about poor battery performance, it feels like a dud. This machine is compact and light weight, obviously meant for mobile use, but that becomes irrelevant if the battery dies half way through the day and you have to tether to an outlet.
On a positive/unrelated note, I do like using the new surface slim pen vs. the standard model, particularly for drawing.
If anyone has any solutions for improved battery life and/or performance tips, please share.