I use Lightroom exclusively to manage all of my photographs and the reason for ever launching iPhoto is to import them onto the iPad or iPhone. It was an often replicated process that I wasn’t too fond of but one I dealt with because I haven’t updated to Lightroom 3 yet. In LR3, you can use the Publish Services feature to do the same type of syncing for you.
But if you still have Lightroom 2 like I do, Matt Kloskowski has developed a preset from which you can create iPad albums straight from Lightroom. It’s a huge timesaver especially if that particular album has more than 75 photos that you would normally have to first export from Lightroom and then import back into iPhoto. Why haven’t I updated to LR3 yet? No specific reason other than to say it’s more of a want than a need at this moment.