Clearly you don't do much on your computer if the ipad replaced it. Some people do more than just browse the web.
What I actually said was that the iPad replaced my laptop, because in situations in which a laptop was the best tool, the iPad is more convenient, and in some cases, has functionality that the laptop does not.
With my iPad I:
• review patients' electronic records
• review diagnostic imaging reports and images, and actually show them to patients (try that with a desktop at the nursing station or a phone)
• review medication dosing and potential interactions
• show patients images that describe what is happening to them or what to expect
• calculate and track due dates
• book and keep track of call shifts and schedules
• keep meeting minutes
• keep track of of messages from colleagues, staff, and residents under my supervision, and
• keep track of billing for services provided.
Of course, it's not just for work, it also is quite useful for web browsing, as an electronic photo album, an ebook reader and a portable movie player and gaming device for the kids when we are on one of our infamously long road trips.
Now I know that the computational power of the iPad is nowhere near that of a laptop, nor is the performance to price ratio. But it does have added functionality and significantly improved portability and convenience. And anyway, the same argument could be used to compare a laptop to a desktop (although that gap is closing somewhat) or to an ultraportable. Convenience always comes at a cost, both in terms of price and in terms of power.
Of course, for those tasks that require heavier lifting or a larger screen, I still have my iMac (I know, some would still call that a toy, but then I'm not doing heavy-duty image processing). But for those tasks that do not require the iMac, the iPad is more convenient than a laptop, and some of the iOS apps are more suited to my needs.