Windows RT essentially splits the MS tablet market in two with Win8 Pro tablets as x86 tablet PCs with touch screens and WinRT tablets to presumably compete directly with Android and iOS tablets in terms of configuration and price. Price being the main reason as ARM based SoC tablets are simply cheaper to produce. The power management compared to Atom based hardware remains to be seen, but I don't see one progressing any faster than the other in terms of thermal efficiency.
I agree WinRT tablets are priced too high to steal significant marketshare from Android and iOS, but we'll see how the consumer market responds in the near future.
Timing-wise, it's unfortunate that whatever you're working on requires a Win8 tablet one month sooner (three if you have to buy one on Oct 26) and probably more unfortunate for MS that they'll presumably be losing a not insignificant number of sales of Win8 Pro tablets by not having them for the holidays, but that's hardly a strike on the hardware itself. It's ready when it's ready.
Personally, I'm not really sure what the market is for WinRT tablets either. Consumers who don't like iOS/Apple. Consumers who have been unhappy with Android solutions. Presumably consumers who are really big MS fans (ie. the ones who bought/own a Zune).
But considering that Surface Win8 Pro will likely be starting priced a good $300 over the entry level WinRT tablet, I'm going to say there's a bigger market for cheaper, albeit pared down, ARM based tablets, hence the two separate line ups.
