I've built a fair number of medium-small sites with it and like it pretty well...I'm interested in your perspective with such a large project. Why do you think it's awfully designed?
I did just run into a pretty nasty and obscure bug. (That was the first though.)
In my case it manifested on ajax calls but not the initial page load. I had a custom grid that worked fine on the first load but blew up when the user tried to page or sort it. And it only happened on production, because the prod server had the component mentioned in the link installed, but the dev and stage servers didn't.
Luckily the guy administering the web servers tracked down the configuration difference, googled, and found the above link, and I was able to make a small change to my code to work around it, pre-calculating the url on the initial load and just referencing the resulting string on the ajax call (specifically, using lexical closure instead of calculating the url inside a lambda). That fixed it.
I did just run into a pretty nasty and obscure bug. (That was the first though.)