Hi Paul, I'm a big fan of Geckoboard - in some circles, your name is almost analogous for a dashboard :)

Getting to over 2500 signups in four months is definitely a great achievement, but I think it would be more interesting to hear about getting to 100 daily active users for example. After all, signups are not worth much if the users don't keep using the service (I'm sure this was not a problem in your case though).

I know there are a lot of generic blog posts and SaaS services for maximizing customer engagement, but reading real stories from founders is always uniquely inspiring.