I think the iPad is a great storage device for photos IF you are shooting JPGs and IF your camera takes an SD card. The iPad will provide sufficient power to the SD card so that the photos can be downloaded to the iPad memory (using the Camera Connection kit). As JPGs, they don't take up a ton of storage space either.
However, if you shoot RAW and/or have a camera that takes CF cards, using the iPad is a lot more difficult if not impossible. While the iPad will display RAW images, the memory is too small for many of the high MB camera RAW files. Aside from the HyperDrive iPad Hard Drive (http://www.hypershop.com …asing-Only-p/iphd-000.htm ) there are no mass storage solutions for the iPad, and that causes a serious limitation for its use as a storage device for travel, etc. if you shoot RAW. CF card support ( http://store.micgadget.com …amera-connection-kit.html ) is iffy at best, and not officially supported by Apple.
I'd love to use an iPad as a storage device, but in it's current form and without mass storage capability, it's really not the ideal solution. You should either go with a netbook computer (e.g., a MacBook Air) with a USB powered hard drive like the G-Tech G-Drive Slim ( http://www.g-technology.com/products/g-drive-slim.cfm ) or with a photoviewer like the Epson P-7000. Cloud storage may also be an alterative, but I've not looked into it in detail yet. I better get cracking, because I'm leaving for Arches NP, the Grand Canyon, Sedona, and Phoenix in a month!