Hello there,
First of all, the overall design is beautiful, bright and esthetically pleasing. I enjoy the use of the bright colors and vector graphics to make the home page more appealing.
Although I do think that there should be more information on the home page. Probably a tabbed format or a simple slideshow to display the main features of the application. I understand you are aiming for simplicity but I personally enjoy a more feature filled application.
When visitors access the "Features" page, you can add a more detailed description explaining how the application works. Maybe a step by step process to setting up the API.
The "Pricing" page is great, simple and answers the most common questions users might have.
The "Developers" page is also very instructive. Although as a PHP developer, I would like to be able to access a wrapper example or a step by step tutorial explaining the process. Maybe a tutorial to match the Demo Dashboard setup.
For the link to the blog, I would have liked to see a dedicated blog for thesunnytrail.com. Seems unprofessional. Could be a simple Wordpress installation with a matching theme. You could even use a simpler platform such as Posterous and create a matching theme.
I enjoyed the simple and straightforward "Dashboard", but the sidebar seems empty. Maybe add additional submenu items horizontally under the main tab bar.The interactive jQuery charts are a must.
Overall, I think this is a fantastic idea and a fantastic application. Great job. I think it will be very popular for any web startup. Good luck!