As someone who switched away from all Google products, including Gmail, I can definitely say it's worth the cost to me. In fact, I'd pay more than the current rate, now that I've had a chance to really use the service. It is fluid and fast in every browser I've thrown at it, including the work-required IE10.

In my opinion, the only thing they could do better is to provide an API for their file storage module, and I believe that is in the works.

You get what you pay for, and while Gmail is a good web client it is far from the best. Fastmail beats it hands down as far as I'm concerned.