IStartedSomething has an interesting take on iPad iOS 5 & Android Honeycomb: opportunities for Windows 8. Some of the points where they say that Windows 8 has the opportunity to make some inroads (italics are my commentary):

[...] Live tiles can offer snippets of contextual information in a consistent format that can be updated without actually launching the application. Developers can also differentiate similar applications by exposing better live tiles.

[...] Having an operating system on a single device that can cater to the best of both worlds independently means you only need one device instead of two to do both tablet computing and traditional PC computing.

To me this is completely missing the point of what a) made the iPad such a hit and b) what made previous tablet computer endeavors (case in point is the UMPC from Microsoft) fall flat, or at least sell barely anything compared to the current "tablet designed OS" tablets.

[...] Only recently has Apple started building social integration into its core platform with iOS 5′s native Twitter functionality.

True, but when Windows 8 debuts it will have been in iOS for as long as it'll have been in Windows 8, and iPad will be on version 3 (presumably) compared to Windows 8 version 1.

[...] One of the weakest aspects of the iOS is the ability to interface with other standard devices and external storage which has encouraged a diverse range of Apple-exclusive accessories. One such accessory, the iPad Camera Connection Kit should be a feature built into every device to make managing simple tasks like browsing and sharing photos much more accessible. I'm confident Windows 8 devices will have built-in SD card readers and the ability to manipulate content on them.

Have to agree here, especially that the camera connection kit should be built in, or at least included and not a $30 extra.

Assuming one can also simply plug in any USB keyboard and mouse to a Windows 8 slate, it will be a powerful capability to have a simple touch experience on the go and a productive typing experience at the desk with the same device and operating system.

Yes this is true, however Windows 8 has shown it's dedication to the "no compromise" UI that basically includes everything, and I think you can pretty easily argue that if you include everything you get something that isn't nearly as useful as a dedicated device. The iPad doesn't have 5 USB ports on it, and HDMI plug and 15 other ports stuck off the side of it, a file browser built in, and 3 different desktop modes, but that's because it's dedicated to doing one thing really well, and it's UI and form factor reflect that. Yes, sometimes it's a bit spartan and it would be nice to just plug in an SD card, but people with devices like this are ok with making that compromise.

That and my apple fanboy-ism aside, there are definitely places where a Windows 8 tablet can take on the iPad and Android Tablet market, and it'll be good to have a third player in the market segment. I just don't think that the direction they're taking with putting everything in one basket will have any better success (even with the new UI) than with their previous windows based tablet attempts.