I've only tried the Spring '05 release of Stagg. I have unopened, Spring '05, Fall '05 and two Fall '06 releases. I've been procrastinating on opening any of the bottles since I have other premiums currently open. My next premium bottle to open was going to be PVW 15 but I may have to pop open that Stagg '06.
The Fall '05 and Fall '06 GTS are both excellent. I would love to hear your thoughts on them side by side! I've never had the guts to open more than one bottle of GTS at a time. In fact, I'm just about considering hiding my second (unopened) bottle of Fall '06 somewhere I won't be able to find it---just so I can rest easy knowing that somewhere, nearby there is always a pristine bottle of Stagg. The mere thought of arriving at a point in my life where I don't have a bottle of Stagg around is a depressing thought.