I would use it to blog while on the go. Here’s why:
My iPhone is with me all the time which is great for writing an entry on the fly (even while walking!) but it’s too small to type seriously and there’s no options for formatting the text (bold or italics) or attaching URL’s on my wordpress app.
My Macbook is portable at 13” but at 2kg still way too big to bring around with me wherever I go. Powering up and preserving battery life is also an issue. I’d rather keep my macbook as my home workstation and keep it for more serious work like photo-editing or 3d modeling.
An iPad would be ideal for typing, less so while walking but more when I’m sitting at lunch, in the train or on the bus. Whenever I feel like typing a blog entry I could whip it out, activate the wordpress app and start typing. I’m assuming that they’d include rich text formatting (and if they haven’t yet they probably will soon) so I could more conveniently do what I like to do: writing down my thoughts as and when I get the inspiration to.
There’s something comfortable about the size, almost that of a diary or notebook which I find perfect for carrying around and writing on. It’s exactly like the notebook that I carry around to jot down thoughts and reminders.