How would I track user behaviors? I'm just using Google Analytics.
All the errors on the site should be fixed now.
It depends a bit on how your site works. A typical use of the GA script may already do the work. But sometimes, you need to set things to do the right tracking: the typical example is the usage of javascript. If you have a lot of JS you may want to track it. Maybe you want to know if some feature is being used or not, you should check those small things and have it clear, so that, when the traffic comes, you will be collecting valuable data about your product. But also, ask your customers. Some human feedback may be much more rich than a bunch of data.
PS: By the way, I like the 'XX shops are currently using Printavo!' PS 2: I'm still getting the error messages (now in the welcome screen).
If you have some budget you may set an ad campaign and split tests to know what's is working and what is not. You may try several different home pages to see which things perform better. This could give you some ideas: http://37signals.com/svn/posts/2977-behind-the-scenes-highri... http://37signals.com/svn/posts/2983-behind-the-scenes-ab-tes... http://37signals.com/svn/posts/2991-behind-the-scenes-ab-tes...
And also: are you tracking your users behaviors? That may give you powerful insights about the product.
I created an account to test it, but I had several errors in a row: 'We're sorry, but something went wrong.'
For the rest, congrats, it looks great. I hope you the best!
PS: You may work on a better favicon with a relative ease, by now is not looking so good.