I have one that I purchased used, but in mint condition. The price was about half that of a new one. It's extremely well-made and nice to use, but a very specialized piece of gear. The problem I have with equipment like this is that it often gets left at home because it becomes unwieldy to take in addition to more general purpose equipment.
The RRS's legs lock in at multiple angles. I haven't used one of the Kirks, but since it's based on a Manfrotto, it's not hard to guess at the quality. It should be very good, but the RRS is in a completely different league. How much that matters is a different question.
Thanks for the links/advice. After looking at the alternatives, I've decided to go with the RRS ground pod. All my other camera support gear is from RRS and I've been very pleased with their products and service.