DO USABILITY TESTING
Often.
Because if those problems were obvious to the OP - they would have fixed them. By definition. I guarantee that everybody here has there own blind spots with there own application or service.
I've been doing usability tests for nearly twenty years now - and the number of times we've found nothing that can be improved can be counted on approximately no hands.
Use online services like peek (there are many, many others too). Do them yourselves. Do them regularly. If I could pick only one thing to help folk improve their product - usability testing would be it. Even above customer interviewing. Nothing beats watching your customers try and fail to use your product.
Here's three books to get you started:
* Rocket Surgery Made Easy: The Do-it-yourself Guide to Finding and Fixing Usability Problems, Steve Krug - Does exactly what it says on the tin. Short sharp guide to getting you started.
* Handbook of Usability Testing: Howto Plan, Design, and Conduct Effective Tests, Jeffrey Rubin & Dana Chisnell - The last book but in much more depth. The first edition of this was my bible when I started doing usability testing.
* Remote Research, Nate Bolt & Tony Tulathimutte - A great guide to how to approach getting the most out of remote usability testing services like peek. The tools are a few years out of date now. The advice isn't.
Seriously. If you're not already doing usability tests go spend an hour or two reading 'Rocket Surgery Made Easy' and then go test your product with some actual human beings. You'll thank me.