Yes, it's expensive... but it sure is nice. The great little G10 has a pleasingly retro look and feel already, and this case, in soft black leather with a red suede lining, really complements it.
From a practical point of view, it fits like a glove, adding very little additional bulk to the camera. Getting to the camera means popping a stud and flipping the cover over, and takes a second or two. If you're expecting to take a lot of snaps, removing the top cover completely is equally straightforward. So much easier than getting it out of any kind of closed bag.
Downsides: if you want to get to memory card or battery you have to remove the bottom part of the case, which is fitted via the tripod screw dock (note that it doesn't stop you using a tripod), but this again takes maybe 20 seconds - I haven't found it to be any kind of problem.
If you can afford it, get it. You won't regret it.