The whole ‘tablets and PCs’ discussion today reminds me a great deal of similar conversations we used to have a decade ago about ‘laptop or desktop’.
That is, someone would ask a vaguely technical friend whether they should buy a laptop or a desktop. And the answer would be “well, how much money do you have and what do you want to do with it?” Laptops were portable but had smaller screens, less power and were more expensive. Which trade-off depended on how you planned to use it.
Over time that break point shifted: laptops got less expensive and much more powerful - today there are very few tasks that need the power a desktop can give, but the screen size point remains (though of course external screens are cheap). And so laptops grew to roughly half the PC market by volume. The desktop market didn’t go away - mostly for screen size or cost reasons (if you’re outfitting an office of 10k people, none of whom take their work out of the office, why buy laptops?)
Much the same analysis applies to tablets today - "what are you going to do with it?" Are you going to do sophisticated, complex, multi-app computing? Lots of keyboard work and detailed manipulation that a mouse is better for? Apps that are only ON a PC? Then get one (whether desktop or laptop). Mostly web, email, games, video, social networks and you’re walking around all the time? A tablet might suit you very well. You probably have a PC too - there’s very little actual substitution right now, but there is an impact on the PC replacement cycle (as well as expanding the pie massively, especially in emerging markets, which is another conversation).
And of course this break point will move as well, just as the laptop/desktop break point did - tablets will get faster and more sophisticated and capable of substituting more tasks. And so we should expect to see tablets taking a growing chunk out of the PC market.
(The other way to slice this is that the PC market is split very roughly half and half between consumer and corporate - corporate boxes will remain longer than consumer PCs, but there’ll be erosion in both.)
Another very important lens to look at this through, though, is Microsoft Office. Office is extremely good (tautologically) at the things it’s good at - there is no credible alternative to Excel for making large financial models and no credible alternative to Powerpoint for making 150-page pitch books, for example. Free alternatives nibble around the edges, and specialised use cases such as statistics have been carved out long ago, but the real threats come from use cases where you shouldn’t really be using Office at all.
This ‘shouldn’t use’ comes from both above and below. Someone said to me on Twitter (I now can’t find who) that their consulting business spent half its time telling people to stop using Excel and use a database and the other half telling people to to stop using a database and use Excel. That is, Excel is used as a business information system in a huge number of companies. It’s a powerful and flexible IDE on its own terms, and this is sometimes a good use, but it often isn’t, and specialized SAAS services will probably carve out an increasing number of these use cases. When I worked at Orange there was a multi-megabyte Excel file on the network drive called, I believe, ‘sum_of_x.xls’ containing complex macros and every major operating metric for the entire company, there for anyone who needed to analyze high-level data. That should probably not, really, be in Excel today.
The same applies to Powerpoint - it’s a very good tool for that 150 slide deck, but what if you’re making a 10-slide deck each week that consists entirely of operating metrics pulled out of a back-end system, manipulated in Excel and pasted into slides, plus commentary, that are emailed to 25 people? Shouldn’t that change from a 2 hour task to a SAAS dashboard and a 30-second task? And would it still need a mouse and keyboard?
(This point also bears on the future of email itself, but that's another topic.)
This carving out comes from below, too. One of these is the Google Docs story, about there can be much debate, but to me the interesting challenge is embodied by this screenshot - the ‘new file’ menu in Excel.