Simon
I just got the Kestrel 58, haven't yet used it fully loaded but I like it, and the fact that you can compress it to fit your kit in a few different ways.
Little touches help are good- pockets on hip belt are a good size, the walking pole quick store are just examples of a well thought out bag. It is also lighter than counterparts but still not the lightest.
My only critiscism is the the "bladder" store on the outside if the pack - in theory a really good idea especially when you need to top up, but I have a Source Wide Pac and where the pipe goes into the bladder can stick into your back a little. So give thought to what bladder you have or looking to get if you opt for the Kestrel