The Metro interface is useless for productivity... too difficult to get anything done with. And the screen was too tiny @ 1920x1080 for using the win desktop. I was forced to use the darn stylus just to click on an icon making the touchscreen useless. Highlighting text (cutting, pasting, moving) was a nightmare. Typing was a pain in the ass with the on-screen KB. Using the add-on KB just turned it back into a weak, slow laptop.
And the metro interface was not well thought out. More like playing with my phone than using a computer. Most of the things I easily accomplished with Win7, I had to hunt for where M$ decided to move it to in the new Metro/OS. Between the discomfort of using the tablet and the uncomfortable OS, it was just too much trouble.
Mostly it was Win8 that turned me sour on the Surface Pro. I'd say it was about 70% dislike of WIN8 and 30% dislike of the tablet itself. Here is Koroush Ghazis' (one of the better gaming/technology writers) feelings of Win8: http/www.tweakguides.com/Windows81_1.html
Pretty well sums up my thoughts.
I'm sure the Surface Pro has some redeeming value, just not for me. My daughter has a iPad I've used a little. Like going from a Yugo to an Audi.