Nice! I got a few cases of Grolsch bottles from my local watering hole a while back, bottled some English Ale with them, and just cracked one open that was hiding in the back of the fridge at my dad's house (og bottled in Nov 08) - it had definitely lost some carbonation. Not bad, but not great. I wonder how long they actually keep beer fresh. So no more beer in them for me.
I'm planning on using them for some Apfelwein though, since that doesn't require the darkness like beer does.