Visual Studio 2005 includes some fantastic UI enhancements over VS 2003. One change that I'm not thrilled with is the Add Reference dialog. The 2003 Add Reference dialog included two lists - a list of available components and a list of selected components. You can easily add multiple references by highlighting them in the available components list and clicking Select, at which point they get added to the selected components list.
In VS2005, the dialog changes to only a single, multi-select list (a single list per tab, that is). This is bad. Multi-select lists have poor usability - especially for very long lists (and the default list in 2005 is about 9 pages, which qualifies as long in my book). Selecting multiple items from disjoint sections of the list is difficult, and its easy to accidentally unselected something that you selected three pages back with an errant mouse click. Adding both COM references and .NET references multiplies the problem - now you multiple multi-select lists. I don't know why MS decided to make this change - in my mind, the 2003 version was much more usable.
On the other hand, the references dialog now includes a "recent" tab, listing recently used references. This is a definite usability improvement.