The latest gadget people are frothing over/poo-pooing is Apple's iPad, a 9.7" screen tablet device which is not available for purchase yet. Regardless of what you think of that specific tablet, a number of vendors are coming out with multi-touch tablet devices and Windows 7 does support multi-touch.
The D.C Public Library has already developed a free iPhone app in early 2009 which lets users search their catalog, and they've made the code available for other libraries to use, so libraries do have some experience dealing with multi-touch interface on a smaller screen. But a larger screen means more real estate for gestures as opposed to controls taking up space - what will this mean for developing mobile apps for the library? And a low-cost device might be an easier pitch than something like a Microsoft Surface - even though libraries are doing cool things with those as well.