I, personally, think it's the best thing GI does still. Granted, I generally don't like when these brewers sell out to the big guys. Therefore, my taste buds may have a hint of bias...
They've done well in promoting it. Add to that, the fact that they have variants, people will eat it up.
Its the first barrel aged stout i ever tried and still one of my favorites somewhat because nostalgia. I agree with you on it being their best offering. I think we are going to continue seeing our favorite breweries getting gobbled up by the big guys. I know if i had a successful brewery that i started and someone offered me a pile of cash id probably take it and retire to somewhere warm.