I've had my iPad for 3 weeks now, and I'm using it more every day.
For taking notes in meetings, including diagrams, it is perfect. I can use OmniGraffle, of if I just want to sketch freehand, Adobe Ideas (which is free) works beautifully. I have made myself a basic stylus (see note for instructions), simply because it feels more natural to draw with something pen shaped, and there is no practical difference that I can detect in drawing on the iPad and drawing on paper, at least in terms of output. And I don't need to haul a laptop around with me - the iPad slips neatly into my handbag, and when I need it, it's on instantaneously.
For the first time in my life, I see a reason to have a subscription to the Safari Online book service. I can read a book as easily on the iPad as I can on paper, and for technical books, Safari is great. I have a lot of hard copy books that I have had to buy in the past, and in many cases I have read less than half the content before I have learned what I needed, after which the book has gone onto my already overloaded shelves. Now I can "rent" a book from Safari, read the bit I need, and not have the trouble and waste of storing the volume afterwards. A Safari subscription costs less than 3 average technical manuals, while giving me access to thousands.
To make this work gracefully, you need the Atomic Web Browser for iPad, which can identify itself to a server as anything from Mobile Safari to Firefox 3 (even IE6, should you be so inclined, though if you are, you probably need help). If you try to use the Safari mobile service using the built-in Apple Safari web browser (now isn't that confusing, guess no one got the trademark on the word "safari"), you will get frequent and annoying interruptions from O'Reilly, protecting their content by making you complete Captchas every few minutes. I wouldn't mind one now and then, but every three screens is excessive. Atomic fakes them out neatly, and this pointless nonsense goes away. O'Reilly folks: get over it, and move on.
In fact, I've written this post on my iPad, while sitting in my favourite easy chair and not at my desk. This is a double blessing, because I have a serious case of tendonitis in my right elbow, and I'm not supposed to use a mouse at the moment. An iPad is tendonitis friendly, which is an enormous help right now. If you have never had "tennis elbow", be grateful: it hurts, a lot.
I have not, so far, lamented the absence of a USB port, or any other sort of port. I have Dropbox, Google Docs, email and as a last resort, cable-based sync. File transfer is not a problem.
The only thing with which I am not entirely happy is Apple's iPad case. I don't mind the design itself: it is light weight, robust and practical. But it shows scuffs. I've had to go over it vigorously with a stiff clothes brush, to return the surface to a tidy condition. However, I can find no other case that I prefer, so I will stick with it for now.
Note: how to make a stylus. First, find, an old-style mechanical drafting pencil, the kind that takes a 2mm lead. Make sure that it has a metal finger grip. I'm using a Staedtler Mars Technico, which you can get from any decent art shop (try Eckersleys, if you are in Sydney). Get a piece of conductive foam (Jaycar, about $AU10 for far more than you need) and a piece of fine plastic tubing. I am using the tubing out of a Swisspers cosmetic applicator, try the pharmacy, or if your significant other is female, ask her. What you are about to do will not damage the pencil in any way.
Take your piece of foam, and cut a slice about 2cm long and about 1cm wide. Make a pin hole in it, and then work your piece plastic tube in about 0.5 cm. Put a small drop of some convenient, thin, fast drying glue to the end of the plastic tube, and push it into the foam. Wait (do email or something) while it dries. Cut the plastic tubing so that there is about 0.7cm or less of exposed tubing sticking out of the foam, and insert that into the lead holder. The conductive foam must touch the metal finger grip for this to work. Trim the end of the foam with scissors, to achieve a shape that works for you, but which does not expose the tubing. You are done now. Hold the pencil barrel so that your fingers touch the metal grip. Your stylus will now conduct the tiny current needed, and it will work on the iPad.