Does your brother have access to a desktop computer? If so he didn't replace a computer for an iPad. He replaced his mobile gadget for a lighter option.
Tablets are great for consumption, but extremely poor for generating content. Even with an external keyword, writing a document (not even talking about a spreadsheet) in a tablet is least than pleasant.
No other PC, just his iPad. And he uses the keyboard and thinks it works great, so you are wrong in saying that it is bad for generating content. That's your opinion, not a fact.
iPad is bad for generating content. I don't mean bad as in BAD. By bad, I mean it's not going to be just as good enough as a PC. Best example? Take photoshop. Photoshop for iPad is so amateurish compared to Photoshop for PC. I can never imagine a designer using just an iPad to survive, because he will miss out a lot of valuable tools (Illustrator, PS, etc.). But, I also want to personally thank you for being so polite and not being staunch (like most of them usually are). Cheers! :)
Hmmm, I'm not being a dick, but I just want to give you an example - As to why word-processing is really difficult on an iPad. Assume you are a blogger, each platform like tumblr, blogger, etc. has its own Editor. And to make text bold, italic, listed, etc., you need to select the text, which is quite frustrating, if not hard on an iPad. Selecting text is easier with a mouse than say, with your fingers, especially on miniscule text.
Selection is just one example. Talk about dragging images within an editor - Most editors don't support the OnTouch event, but rather just the OnClick event, so there is a huge difference, actually.
My brother just tossed his laptop for an iPad and he loves it. There's one person who has, so you're already wrong.