This is a little back favor to the community of HN which helped a lot with feedback yesterday. Thank you all for helping, this post describes our experience with testing the Popify site.
We use PHP/HipHop/Redis and nothing else. The server can do 1500req/sec.
The traffic today is about 30 users per hour without additional exposure. We'll do a proper PR campaign in a few days but have some user requests to implement right now.