Unless anyone had other suggestions for a meetup in Berlin, I'm going to suggest meeting at 'BrauHaus Lemke' in Hackescher Markt in the centre. It's really easy to find and has good beer. Web address is
http://www.brauhaus-lemke.com/index.php?area=1
I'll be there from about 17:00 I think, then get the metro to Columbiahalle around 19:00 when the doors open.
If anyone wants my mobile no., PM me.