I’ve always taken my own bike out there on the grounds that I know how it handles, I don’t really want to be getting used to a new bike on much steeper more hardcore terrain than I’m used to all at the same time!
Having said that I used a Hemlock for a day when I was out with AQR back in September 08 and it was nice to ride something different.
Hiring a bike out there does mean that you avoid the £18 each way fee that Ryanair/EasyJet charge for bikes now and it’s a lot less hassle at the airport. But having your own bike out there means one less thing to worry about, you know it’s set up just right for you and you know how it rides/handles.