I'd like to do a poll and find out how many Surface users do or don't use Android or iPad as their tablet.
I have a Nook HD+ (Android), an iPad 2, an RT and an SP3. I use all four as tablets, mostly for reading/writing emails, reading other documents, surfing the web, watching videos, listening to music and playing chess or solitaire. I also do most of these things on my Windows phone.
My Nook is the lightest of the four tablets, which is a real advantage. It also has an accessible file system, so I can download and transfer all kinds of files. The file system also makes it easier to watch videos and read documents on my Nook than on my iPad. The iPad is my oldest tablet and has aged amazingly well. Its battery is still going strong, while the Nook's battery tends to peter out far too soon.
Lately, I've been using my RT the most as my tablet. This is probably because it has a larger screen than my Nook or iPad, and its battery last long. I like the fact that the onscreen keyboard doesn't use as much of the screen as with the smaller tablets. Plus, the keyboard has cursor and control keys which make it easier to respond to emails. I can also use Word to edit short work documents while lounging at home.
I occasionally use my SP3 as a tablet, but it's overkill and my smaller machines work fine.