How important is finding an UI bug?

There is often a debate among the testing community, which bugs have more value , a UI bug or a functional one? Most of the QA folks have this opinion of functional bugs being more important than a UI bug.In general UI bugs are more important for consumer applications and functional bugs for the enterprise applications.A functional bug is considered more important because that is what is expected out of the system and if it fails there is no point in having a system. Not everyone is tech savvy nor everyone will check for the functionality when you ask them to use it for the first time. Let us for example consider someone using an e-commerce website. When users click on the link,they would first look at it for its aesthetic appeal. It doesn't really matter to them if the site's functionality works fine, the transaction works fine etc etc.,  The first few seconds to minutes  the site should be appealing for the end user like showing the latest collections, the current offers,a catalog of the products listed etc. If this part has any issues, then it is going to screw up the organisation big time. If clicking on any of these links, takes the user to some 404 error or 500 error, then the user would no longer remain in the site and would move to some other sites. The next important thing is how good is the usability of the website. When I say usability, it means that how easily can someone use the website to perform any transaction. The functional part comes after all these. Adding/Removing any item to a cart, proceeding to checkout, making payments etc come under the functional part. All these are expected to work fine as they are the basic features of the e-commerce website. Any website that makes a user to stay on it for a long time is sure to have a good user interface.  Even minor  UI bugs can make or break opinion on any product.It is therefore very important that UI bugs be given equal importance when testing any application.