1. What am I mainly going to use my new Surface for?
The biggest difference between the Surface RT & Surface 2 compared to the Surface Pro (1 and 2) is that the Pro is a full fledged laptop PC. The Pro has the ability to run desktop apps such as Quicken, Windows Live Essentials, and Google Chrome as well as run Windows 8 apps. The Surface RT and Surface 2 do not have this ability; they are only able to run Windows 8 apps (also called Metro apps).
This is important because if you need to run desktop apps on your new PC, you will have to get either the Surface Pro 1 or the newer Surface Pro 2. If you do not need to run any desktop apps, great; you can settle for a Surface RT or the new Surface 2.
2. How big of a screen do I need? Will I be able to operate my Surface without straining my eyes too much?
This is a problem that I have ran into quite recently. I have a Surface Pro (the original) and I really enjoy using it. It has a 10.1 in. screen with a 1920 x 1080 resolution. The amount of screen space you need really depends on what kind of work you plan to do on your Surface and how good your eyesight is.
For example, I have a web design business (Sam's Web Design; check it out with the tab above), but I rarely edit my webpages on my Surface Pro. Why? The answer is that it is much easier for me to have a dual monitor layout (one monitor for code and the other for a preview). The Surface Pro can be hooked up to an external monitor, but the issue lies with how big items appear on the screen. Windows has a built in scaling feature (which happens to be turned to 125% when you first open your Surface) that can help alleviate this problem. I have kept the window scaling at 125% since it is much easier on the eyes while still retaining the native resolution of the screen (translation: things look crisper and smoother on your screen). You can enlarge items even larger, but this will impede how much you can see on your screen at once.
3. How's the Surface support?
This is a very easy question to answer! My experience with the Surface support staff has been great (They have replaced my Pro once for a faulty Mini DisplayPort) and they helped make the transition to the replacement as simple as possible. They even extended my warranty so that I would not have any delays during the process!
In closing, I will just say that the decision to buy a Surface is really up to what you plan on doing with it and how much you have to spend. I would definitely recommend getting one, but I would rather you have a PC that suits your needs.
Post in the comments if this helps you in any way!