I think it’s generally accepted now that in ecommerce faster sites convert better. For many startups, though, investment in improving site performance need to be weighed up against other initiatives that can improve growth or profits. Here’s some data that can help in that decision (courtesy of VentureBeat).
These are meaningful numbers, but I was a little surprised they aren’t higher. At the early stages improving things like merchandising, design, email campaigns may have a bigger impact. That said every good ecommerce company has a fast site and speed impr0vements shouldn’t be put off for too long.