Microsoft Surface completely beats the iPad in terms of word processing application. I tried to use the Page with on-screen keyboard, but it is awkward in anyway.
Personally, I can use Pages with the onscreen keyboard just fine. Mind you, I tend to write in short bursts of 20-30 minutes at a time, mostly due to time constraints. I've considered buying a keyboard for it, but when I *do* end up writing for longer spans, I'm inevitably in front of my computer anyway. (The only feature I miss from the desktop version when I'm using the iPad version is the ability to edit styles. The full set of style options seem to work just fine when they're set up on the desktop version, but there isn't yet the ability to *change* them on the iPad.)
But, there are keyboards available for the iPad which are as good or better than either of the standard Surface options, including keyboard cases that don't involve carrying around a separate piece, and most of them will work perfectly well with the keyboard sitting on your lap, or holding the keyboard and iPad in one hand while you type with your other. (Personally, I think the onscreen keyboard is a better option in that scenario, though.)