Has anyone that upgraded from the Surface Pro 3 to the 4 'regretted' it or the opposite? So thrilled you are glad you made the jump? Lightly used Surface Pro 3 - i7 - 8 gig RAM, keyboard, etc - I am seeing for less than $1k - This same price is what Costco and others (Black Friday Deals) are selling the i5 Surface Pro 3 and the Surface Pro 4 without the keyboard. Thanks! - trying to decide which way to go but not spend foolishly.