There are a lot. I think that the Client Access Model is really going to change how interaction with SharePoint will occur. I can see a fully Windows based SharePoint in the near future. However, my favorite change is the new notification area of the User Interface. For those that are not familiar with it, compare it to the pop-up that shows when a user logs into Live Messenger or Communicator. There is a pop-up that shows for a small amount of time telling you that someone you care about has logged in and then it disappears. It is fairly unobtrusive but quite useful.
The notiifcation in SharePoint 2010 acts pretty much the same way. You get a little message showing up inside SharePoint that you can act on or ignore. The best part is you can write code to show your own messages (I am not sure what messages are there by default). There are many, many ways to use this. Some that I can think of off the top of my head is a user login notification, new document notification, new task notification, and so on.
I am sure as I use SharePoint more and more there will be other new features that will catch my eye but this is my favorite....so far.
For those who do not know, a stylesheet, AKA CSS, is used to help define the look and feel of a web page. Check out the CSS Zen Garden for some great examples of what CSS can do.
While working on a recent project I noticed that the incredible web page I created did not look quite so incredible at the customer's site. Some things would be off by a few, or not so few, pixels or images were just not showing. To make a long story short their MOSS custom master page called a custom stylesheet which changed the way of a lot of stuff I designed worked. I did get everything working and looking right but it did not make me look quite as good to the customer as I would have liked. I should have gotten a copy of their master page and stylesheet before I started designing. So much for first impressions!
This experience can be used in real life. While people and companies do not have stylesheets defining how things look and feel they have corporate standards and just "that is the way we have always done it" that do. While your job as a consultant or even as an employee is to do the best possible job possible you need to understand that the company's "stylesheet" may make what is "incredible" to you not incredible to them. You may want to create the world's best web site using AJAX, JQuery, Silverlight, and many other buzz words but the company is still on I.E. 6 or may not authorize the use of Silverlight. Your job is to make your "incredible" work in their "stylesheet" and perhaps make recommendations and suggestions as to how to change. That is what changes the consultant to a trusted advisor.