Likes:
1. Flexibility: Can be used comfortably as a tablet, as a "normal" notebook sitting on a desk, and in all sorts of contorted positions in a lounger, on a couch, in bed, etc.
2. Screen: even with the yellow hazy line along the left-hand side, the screen is lovely. Accurate colors, incredibly sharp, and the 3:2 ratio is so much better than 16:9 (maybe even better than 4:3 in some ways, e.g., for video).
3. Input: I don't use the pen as much as I did back in my Tablet PC days (different jobs), but when I need it, it works. And I love the feel of the Type Cover--probably my fastest typing device, taking over from the MacBook Air.
Dislikes:
1. Update flakiness: I still get the 10/6 hardware update popping up and installing, requiring a reboot. And I hate to leave updates uninstalled, for whatever reason. And I don't really have that issue with my other machines.
2. Fan noise: This could actually be a positive depending on use-case. As a notebook, fan noise is superior (my MacBook Air, for example, is much louder, and don't even get me started on my wife's HP Envy 14). As a tablet, though, any fan noise is unwelcome since we've been trained that tablets are fanless.
3. Heat: Same with #2. As a notebook, the little bit of heat that I experience (sometimes more than a little, but not often) is irrelevant because the SP3 doesn't come in contact with body parts as a normal notebook does (again, MacBook Air, I'm talking about you). As a tablet, though, it's warmer than my others (although my Nexus 10 does get toasty on occasion), particularly to the touch on the screen (it's really the only tablet I've used where I can feel warmth on the screen vs. just the back cover).