There are a ton of third-party keyboard options for the Apple iPad and I have owned many of them. No matter how good they are, they can't compare to the utility and functionality of the Microsoft Surface Type and Touch Cover options and this is primarily due to Apple's limited support of these keyboards.
While using a stylus on your tablet is a great way to take notes in meetings (a much less rude experience than having people hiding behind displays) and while walking around (I see tablets in the medical arena all the time), nothing beats the efficiency of a good hardware keyboard. Unfortunately, Apple hasn't yet embraced these external keyboards in iOS so the experience is a disjointed one comprised of two-handed typing mixed in with finger taps on the display.
On the other hand, Microsoft's Surface and Surface Pro devices are optimized for external keyboard input and Microsoft makes a couple great options for consumers. The Surface platform is so well integrated with keyboard support that I think Microsoft needs to start including at least one variation with each Surface purchase. Surface owners should not have to pay an additional fee to buy a keyboard and including one would address many of the complaints we hear from potential buyers.
Our ZDNet tablet guru,, has tried more iPad keyboards than I have and is able to be quite productive with them. In terms of writing, I agree that you can be productive with an iPad keyboard and a good text-editing app like IA Writer or Pages. But try doing much more than writing, controlling media playback, or launching just a few apps via shortcuts and you quickly see that the iPad keyboard experience is limited.
I assembled a post onlast year and these all still apply today. In addition, the new Surface Pro 3 touchpad is vastly improved and provides you with an excellent cursor/mouse controller right on the keyboard. I can actually do everything on my Surface Pro 3 with the keyboard without ever having to touch the display, which is definitely not something you can say about the iPad.
While the iPad can be used by some people for their specific work tasks, I still find it to be much more of a media consumption device. The Surface 2 provides you with many of those same media experiences in addition to advanced keyboard support with Office and more. The Surface Pro 3 has no limits and provides you with the ultimate portable keyboard solution.