My only hesitation in this is that to me one of the key defining terms of a tablet is the word "Instant." Will the Windows 8 tablet be instant from sleep mode? I know if I reboot my iPad or Transformer it takes 30 seconds or so before I can use it but that may only happen every few days. I'm talking about every time I close the lid. For instance on my laptop I open the lid and press a button and it takes 5-10 seconds to wake up to a point that I can start using it but on my tablets it is instant!
Since the Surface tablets run on Windows 8 and its ARM version Windows RT the boot and resume times will be very fast. Windows has focused on lowering these times on cold boots of ~30 seconds or less and instant resume. With flash based hard drives you shouldn't see anything different than any other tablet/smart phone for resume times (i.e. instantly).
It is really difficult to say how the RT tablet will do compared to an iPad. It really depends on how well it does PC tasks and how much it can draw from the general Windows eco system. If that eco system is limited to WP app then it is in trouble until they can build that out and will lag Android and iPad just like the Windows Phones do.
Because the Windows 8 version is a true PC I think it will kill the iPad in many scenarios and even take a bite out of the Macbook Air. There is pent up demand for a true PC tablet and this thing is ready to blow up for all sorts of applications where iOS and Android fall short. In traditional PC markets where people have been making due with iPads in place of PCs this should make a big splash.
IMO I do believe the the Surface will steal a lot of the Ipad users based on it current capabilities, but not only it's current capabilities, but what they have brewing in the near future. You have to remember they showed you what it can do now, (which is my opinion blows away Ipad out of the water already) but think of apps that can be added, think of the extension that i will have such as: connecting to an Xbox with the new announced Xbox Smart Glass, their music selection, and the possibilities to monitor network infrastructures on a business level. The skies the limits I think. Microsoft Surface will be the new standard of what a tablet is supposed to be IMO.