I haven't tried it, but Charlie Papazian has; a recipe with "lime leaves" is in his Homebrewer's Companion book. I'm sure he must mean kaffir lime. the recipe is called Coconut Curry Hefeweizen, with ginger, red pepper, coriander, fenugreek, cinnamon, coconut and kaffir lime leaves.
Check out the new brew from Stone Brewing. It's stuffed with keffir lime and is a HUGE Belgian style. It's part of the limited series of beers that are intended to be kept 10+ years. I liked the lime...I imagine it'll smooth with age, but honestly I'd prefer coriander for a lemony zing flavor. The keffir was a bit heavy. My wife has a great keffir lime tree, though, so I may try some at some point.
I had lemongrass in a beer called Monkey Knife Fight at a pub in Philadelphia. Sorry, forgot the name, but there can't be too many lemongrass beers called Monkey Knife Fight out there It was OK...again, I think the brewing tradition for lemony spices has focused on coriander for a reason. YMMV.