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Generally, I tend agree with you, but your examples are really weak. "they have letters to type, personal accounts to tabulate or photos to crop and print." These are all things that webOS could easily excel at. Heck, have you taken a survey of all the online office suites and photo-management tools out now? Many of them approach the functionality and power of native software--and manage to perform snappily while they're at it.
For "creatives" such as myself (a developer and sometimes musician) it will be a long time before the traditional desktop can be replaced. For many average use cases however the barriers are blurring fast.