Dedicated Appliances not General Computing
Multi Touch is the future of UI. People are trying to apply multi-touch to the technology and standards of today... which is why it doesn't make sense.
PC's as they exist today will be seen as relics of the past.. sitting at a desk or with a computer in your lap for hours doing all your work and entertainment? Why?
"Computers" will be decentralized, casual use and specific use devices ubiquitous to our daily lives.
Touch is already huge with dedicated devices AKA appliances... like GPS, hi-end kitchen appliances, point of sale terminals, etc.
Multi-touch will become more standard with these devices but will also be used for General Computing... but not the way we do it today...
Touch UI works for almost everything except word processing. It works for graphic design, game play, navigating menus, flipping through text 'pages', photo albums, music collections... anything that is basically read only.
When you add in auto-suggest for things like searching and filtering it works for web browsing in general... ie: type the first few letters then pick your selection as it rises to the top, no need to type out the entire sentence/keyword set.
There definitely will need to be a move away from typing intensive tasks, letting the computer do most of the work with the operator gently guiding and suggesting via a touch UI which decisions it makes along the way.
I can see all sorts of drag and drop UIs that let you build queries or task lists similar to how Automator works... all kinds of preset building blocks that the user wires together to create their own personal workflow. Once you have selected a general direction for your task (Spreadsheet, Online Purchase, Photo Editing, for example) there are only so many options left... and a wizard interface would be very quick when you are not moving a mouse around the screen and instead are simply jabbing at the options with a finger.
I don't think most people can really imagine what a great Touch UI would be like. They are so oriented to doing all the work themselves using a keyboard and mouse that they are blind to how much extra thought processing goes in to the hand-eye coordination required to even do the simplest task using a mouse....
****where's my cursor, okay found it by waving the mouse around, now get it over to the window, click to focus, now position it just over the item I want to click on, click once (not twice, don't want to open it) to highlight it, now right-click to bring up the context menu, now ease that cursor ever so slightly over to the right and down so that the rename item is active, now click once. whoooh.... got it, oh crap don't click anywhere or I'll have to redo all that right-click stuff... okay now start typing the name and.... hit enter. Good now my file is named WTFTookSoLongToRenameThisFile.****
Multi-touch version:
****Cursor what cursor... there's my file, -touch-, got it selected, now I'll hit the edit file menu, -touch-, good it's open... now tap "rename file", ok that popped up a dialogue with a keyboard, tap-tap-tap "ThisWasSoFreakinEasy" and done.