I'll second all the above

We've used it a lot and it's a nice bonus on top of the usual miles. It's also a very small staff (just 4 of them I think) so you get to know them and they are extra helpful.
One tip is to make sure that if you try and book a "space available" upgrade that you print and take the email with you to the ticket desk so they make sure they have you on the list.
I'd be interested to know how a Flying Co upgrade request compares to a Flying Club upgrade in priority as well. I was at the gate at LAX in July along with 8 other people waiting for a miles upgrade to UC (presumably all Club rather than Co) and I was the only one to be upgraded. I am a Gold and was on W class ticket though.