iPad has plenty of useful applications for multiple purposes; coupled with an unlimited 3G data plan, the tablet is almost there to be an all-around laptop replacement for productivity/utility purposes as well as media and entertainment use (its real forté). Almost. Typing with the virtual keyboard is really painful for anything except short notes like status updates in social media, or quick email replies. Since iPad supports bluetooth, it is perfectly possible to use it with full wireless keyboards. I have been using the Apple Wireless Keyboard for this purpose some time now, and it has made a real change in terms of usability for writing, of course. Unfortunately the iOS does not support keyboad shortcuts except for some basic actions, like copy-and-paste. I have not found a shortcut that would switch between applications in cmd-tab style — iOS 4.2 supports multitasking in iPad, after all. No way to go to the home screen and launch applications with keyboard only, either. Typing email with the keyboard is fine, but to send the message, you need to tap into the touch screen. The final resulting use experience is a sort of weird hybrid, having features of PC style interaction, and tablet/touchscreen actions, all mixed together a bit uncomfortably. But after some practice you can get it, I guess. The final lesson is newertheless that iPad is not intented as a full laptop replacement, and putting some extra money can you get something like the new version of Macbook Air, where keyboard and screen are already fitted together with an OS that supports a real desktop environment. But if your laptop is taken away for repairs (like my case), then you can get away with iPad and an add-on keyboard for some time, with some extra effort.
frans goes blog 
There are a couple of major issues in iPad that make it look like Apple has made an explicit decision to cut down its ability to function as a productivity device. Both are related to iOS. Firstly, since there is not any kind of file management by default, it is very difficult to copy or move back files that you have been working on in iPad. It is easy to access them through Dropbox, for example, but saving to the cloud after even a minor edit is a hurdle. You have a workaround though: e.g. in Pages, send the file to yourself as an email attachment, then open/save the file in GoodReader, go to GoodReader’s Manage Files and there copy it to your Dropbox. Not entirely intuitive – there is a step-by-step guide here: http://www.wisecwa.com/digitaloffice/?p=601 .
Another issue is that you cannot share the screen of iPad, even if you go and buy the official iPad VGA Adapter. Apple has decided to implement the “external screen mode” only in an application like Keynote. An external app like 2screens can help to a point, but it is not the same as true screen sharing. http://itunes.apple.com/us/app/2screens-presentation-expert/id370913954?mt=8