Announced at Dreamforce is a new UI for Salesforce!

This new UI will of course be optional, but addresses a number of issues with the current UI.  What I've seen so far is impressive.  It definately looks cleaner and does a better job of presenting data to the user. 

One of my favorite features was an enhancement to add a few indicators at the top of the opportunity (I'm hoping it will be available for all objects) to show the most important data about that record.  In just a few seconds, you can easily see what's going on with the record.  They call this new feature the "Deal View" and it will be customizable.

The Related Lists have also been moved over to one side and make for a much cleaner interface and usability.

For developers who've built custom UI to look and feel like Salesforce outside of the standard Visual Force pages are going to have some issues as well as those who've built Flex UI to match.  However, standard Visual Force pages will easily adopt the new UI.

The new UI has been designed so that it's fully built out in CSS, but the developer community will not have the ability to change the CSS, at least not in the near term, but I wouldn't be surprised to see this in a later release.  Also, it should be noted that they aren't changing anything in the Setup section.  Thank heavens, because this would just confused those of us who know the setup area inside and out and need to produce applications for our customers in record time.