I've been thinking about going this way as my work mobile device.
The main things I do on my current mobile work laptop (Mac Book Air) are:
Email - no problem with that, seamless apart from the ease of attaching files, but hopefully that will improve;
Internet - again, no real issues with only the occasional website not being supported by Safari;
Office documents - with the addition of a wireless keyboard, I can get by with the iOS offerings (Pages & Numbers) for simple documents, but the file management is cumbersome and lacks the simplicity of opening/saving/importing/exporting of documents that is part of everyday life on OSX or Windows;
Photo albums - the iPad is ideal for this;
Presentations - I haven't yet tried Keynote on either the iPad or Mac, but the reviews do look good, again apart from file management issues. It appears that with the addition of a VGA adapter these can be displayed on a projector and can even be controlled using an iPod or iPhone as the remote.
So I'm almost swayed if the file management can be improved on the iPad, but at that point I'd be wanting to store all my data on the iPad and I'm already close to the limit on my 128GB Mac Book Air. So, bring a 256GB iPad with better file management and I'll be sold!