I am about to embark on a 12 month round the world trip, and thought the iPad would be a nice addition for me. I have lots of digital ebooks of popular travel guides like Lonely Planet, Frommer's, Rough Guides and DK Eyewitness, etc and they work really well with GoodReader.
I got a 64GB 3G model, I don't really want to pay for a separate SIM card as I travel, however the GPS is the reason I got the 3G model. I have jailbroken my iPad and all my experience from the iPhone has come in very handy. Actually now I don't know what to do with my iPhone, it has been very neglected the past 2 weeks, if I could get a decent price I would sell it, but I will just keep it for tethering and for 32GB of music and for emails and Reeder.
I was backpacking for the last 6 months with my iPhone 3GS and a small touch netbook, the Kohjinsha SC3 with atom processor and 7" single touch screen, but the battery life sucked, I had to carry an external battery which weighs about as much as the iPad, and it was not good for reading those ebooks. I finally got sick of waiting for a proper touch interface, with Android not being mature enough, and Windows 8 a long way down the road. So I caved in and bought a giant iPod Touch
So now I will leave the external battery at home and just travel with the iPhone, iPad and the SC3 Windows 7 machine, and use the SC3 for iTunes, photo management, Chrome and Firefox and of course USB ports for the 1TB of content I am taking with me.
The worst thing so far with the iPad is how iTunes looks on a 1024x600 screen, very meh. I also don't like how the API for the keyboard is locked, so I cannot have smaller keys but have an extra row for numbers, or have a TAB key. I also had to turn off backups because they were so slow. Besides from that it is lots of fun.