When you watch the latest ads, Microsoft is trying to communicate a message that the new Surface Pro 3 is a device for Mac users who own (and have to carry around) both an iPad and a Macbook Air.
Essentially, they're conceding that Apple is still the "one to beat" in the tablet market -- and they think their best shot at improved sales is cannibalizing sales to people who invested in the Mac ecosystem with multiple portable devices already.
To me, that says "niche player"!
I think almost everyone agrees that the Surface has good hardware specs. Essentially, you can order it configured with all of the same options you can get in an Macbook Air (up to 8GB of RAM and an Intel core i5 or i7 CPU), so it would be no surprise if it performed every bit as well as one of those.
The problem is, MS still wants you to believe you should pay the high price of a Surface Pro 3 (compared to an iPad at least), because it will do double duty as your tablet and your laptop computer. I'd say that's not so compelling! I own an iPad Air with wifi and cellular data, and I also own a Macbook Pro notebook (issued to me by my employer). I take the iPad Air with me all the time when commuting to/from work, but I use it for things like reading the digital version of the morning newspaper, checking my new email, and maybe playing a casual game like Words with Friends. My notebook stays in a dock at work unless I know I'm going to some destination where I want a full blown computer setup for some length of time (like a business trip or a vacation, where I'll use it in the hotel room).
I'd rather not carry around a device with a keyboard attached if I'm just using it for reading and a little bit of web browsing, and I like the fact that even if my iPad gets broken or stolen, I have all of the really important data back on the notebook computer -- so it's not a big problem.
In a scenario where I was really going to be doing a lot of mobile work? It'd also be a plus to own and have BOTH devices with me, since that means at least double the battery life available to me without a need to recharge.