I've just spent a week using a Surface RT outfit on loan from Microsoft, from which you'll gather that I didn't rush out and buy one -- unlike many of my ZD Net colleagues. While I enjoyed using it, particularly as a tablet, the loaner didn't change my mind. But if you're thinking of treating yourself for Christmas, or whatever, I can tell you that the Type cover is a good deal.
The first thing I did with the Surface RT was test my typing speed in words per minute using one of the online services: typeonline.co.uk. If you'd asked, I'd have said the Type cover felt a bit slower than a "real" keyboard such as the Microsoft Comfort Curve 2000, which I happen to be using at the moment. When the result came up, I was surprised to find my Type cover score was 1wpm faster.
With the standard, non-responsive Touch cover, my typing was two-thirds as fast, and I didn't really enjoy the experience. You can probably get used to it, and thus narrow the gap to a "real" keyboard, but why would you? The Type cover is only 6mm thick, compared to the Touch cover's 3mm, and there is no practical value to the extra thinness.
Trying to touch-type directly on the Surface RTs screen was a bit of a disaster, and my wpm score tumbled to only 40 percent of my normal speed. I usually resort to more of a two-finger style with onscreen keyboards, because screens are not very good for touch-typing. (You can't rest your fingers on the home keys.) I was a bit surprised how low my score was, though it was still rather better than the 25 percent speed I managed with the same test on my Google Nexus 7.
Both keyboard covers are extremely convenient to use, because they click on and off in a second. I found this contrasted with my use of an Asus Transformer running Android. With the new hinge design, it's very easy to remove the tablet part of a Transformer from the keyboard dock, but not as easy as with Surface RT. The result is that you do it much more often, and thus make better use of the device.
The Surface's built-in kickstand is another very convenient feature, and thus gets more use than a separate stand. The drawback is the fixed viewing angle. I would often have preferred the screen less upright, which is simple with a laptop, and more or less impossible with the kickstand. (It might be even worse if you're taller.)
The Surface RT is such a gorgeous bit of hardware that I might still buy one, but it would probably be a Surface Pro with an Intel processor. In effect, this would be a replacement Windows laptop that happens to come with a "free" tablet. However, I suspect I'm more likely to go for a touch-screen Asus or Lenovo PC that works better as a laptop than as a tablet. Good as the Type cover is, by tablet standards, I wouldn't want to use one for the extended keyboard work I often need to do.
Surface RT is a great tablet, and it has a much better user interface than either an Apple iPad or an Android tablet. It's also more than a tablet, and the bundled Microsoft Office and a Type keyboard means it's capable of doing real work both for home and enterprise users. However, it's still a bit less than a real Intel-based laptop, and more of a companion device than a replacement.