I stopped using a laptop for business travel 3 months after the IPhone came out. I gave up my personal desktop and laptop in March of this year. I found that 95%+ of my laptop/computer use outside of the office (even business travel) was for reading and responding to email. The few occasions I need a desk top during travel I've used one at the company I'm visiting or the business center of the hotel I'm staying at. I up load large files to MobileMe and use a document reader app on the IPhone. So far its worked out well and I enjoy not having to carry a laptop when I travel.
That's pretty cool you can do that.
But I write documents while I travel or work from home and occasionally have to access our SAP system and files on several servers. So my laptop isn't going away in the next 18 months unless an MS Office iOS version comes out.
On planes I see people with iPads and iPhones playing games and watching movies, people with Blackberries reading and writing email, and people with laptops using MS Office.
That MS office stuff what the tablets really need to address to kill the laptop.