I'm neck deep in a book about Pages on the iPad at the moment, which is why I've been a bit light on LR-related posts here. But the upside is that I've been spending a lot of time shuttling photos between my Mac and the iPad. As it turns out, there are lots of ways to move the photos back and forth. Some are hard, some are easy. One of the most common, unfortunately, has a big drawback.
That's because it involves using iTunes to sync an exported folder of Lightroom photos from your main computer to your iPad. Unfortunately, as the iPad's now set up you're pretty much stuck choosing to always use iPhoto or never use iPhoto as your photo source. That's because if you choose to designate a sync folder for your Lightroom photos, any previous synced iPhoto albums get wiped off the iPad in the next sync. And if you switch back to using iPhoto as your source, then the Lightroom photos get wiped from the iPad.
Neither is a disaster: You still have the iPhoto and Lightroom shots on your main computer. But it means you can't have a mix of iPhoto and Lightroom photos appear within the iPad's Photo app. More soon on possible workarounds.