Well, I bought and use the iPad as a supplement to the Surface (RT) and my desktop machine. I see each platform for the strengths that it has and the way they combine to make my life easier. There is no doubt that the iPad is an excellently crafted device, which is made all the more attractive with its app eco-system. However, since I have very specific needs from my iPad, my exposure to the iOS app eco-system is very limited - but what I do have work very well.
Similarly, the Surface, in my context, performs a very specific function and it does it very well. Again, I have limited demands from its app eco-system, which is why the alleged sparseness of the app store (now very much improved that what it was when I got my Surface, which was close to a year back) did not and does not bother me. I am equally appreciative of the build quality of the Surface and the way it generally handles. It's accessories - while like Apple's is relatively expensive - are excellent! (My specific reference is to the Type Cover, which is one of the best keyboards that I have used and here I am comparing it to some of the classic ThinkPad keyboards that I have used and that I currently use).
In short, I spend very less time - if at all - comparing the iPad to the Surface; rather, I spend most of my time working out ways and means by which each enhance the other's capabilities and how they may - individually and together - contribute to my work and other needs.