I think I was singing the praises of my Surface Pro 4 last time I was in this thread.
Some time last year I dropped mine on a marble floor and fucked the screen. Paid their extortionate fee and sent it away. You get a renewed warranty with the new one, which I thought was decent. It was clear straight away that the refurb that they sent back was much slower than my original device. Eventually it started having issues with overheating and the screen flickering and basically became unusable. Sent it away a couple of weeks ago and got given another refurb. Also slow as fuck, and within a week or so it's crashed and now completely refuses to turn on.
I've looked about online and it's a common issue. The refurbs they send out as replacements are seemingly pieces of crap more often than not. You've basically got to keep doing it until they send you one that works.
Wankers.