iOs & iOs Apps (inc iPhone, iPad, iPod, iBrick)

I have one which I use almost exclusively. The Netbook hardly ever gets used.
I tend to use it for mail, web, reading books, PDF manuals and comics, making notes with Evernote, making spreadsheets with Numbers, knocking up musical ideas with Garageband and watching movies and TV shows.
I think you still need a real PC or mac. The iPad is not a desktop replacement (It has not Flash, and having no user-accessible file system as such it can't even download many files from the web), but it is a laptop replacement. I still have a powerful desktop for music production, image editing, huge filestore for MP3s (and the iTunes is shared so I can play them on the iPad - with Airport Express plugged into the stereo. nice)

However, I have found it enormously useful to make sure I always own at least one OSX machine (my Netbook is a hackintosh) to edit PDFs on.
Preview makes rotating and cropping single pages really easy, and a lot of PDFs have an image format that doesn't work in iBooks. Opening them in Preview and saving them fixes these problematic PDFs. Some apps also have iOS "extras" (such as the comic book reader I've got which has a really nifty iOS app to transfer content). I also keep one old Windows XP laptop, for reading those troublesome (especially copy-protected) discs that won't work on Windows 7, plugging in old devices (e.g. anything with a serial port).

you tried GoodReader for iPad? Its a PDF-based revelation.