- Performance. VS2010 is the first non-gaming application that has ever taxed my laptop to the point where the fans run all the time. Granted, the laptop is 6 years old, but I can vouch for it as a workhorse (I hope all of you Dell 600M owners can relate to this). I can imagine this application is a literal drag on battery life. As someone who loves to program on the go, this will probably be hindrance. Of course, I haven't done any benchmarks to move this from the realm of the anecdotal to the realm of fact.
- Closing Files. In VS2005 and VS2008, file tabs were closed by clicking on one shared button in the top right corner of the editor window. This meant that you could close a large number of files quickly by just clicking on that button repeatedly. VS2010 places the close button on each individual file tab. To close windows, you have to move the mouse to each tab. I know you can right click on a file and close all other files, but this is not the same as allowing me to close the files I choose to close in a quick and easy fashion.
- WPF UI. The first thing I like about the fact that the UI was made using WPF is that Microsoft has invested in it's own technology. I hate the term "dog fooding"; it conjures up images of lovely domesticated animals being slaughtered to create shapeless pieces of meat. But Microsoft is eating it's own now and that means they feel the same pains we feel. The second thing I like about this is that it provides an example of what can be accomplished with WPF when developing business applications beyond image galleries and media streaming applications. I don't know about the other Average Joes, but there has not yet been a point in my career where I've had to create a streaming media player. Embedding Media Player into my application, yes. Recreating Media Player, no.
- ASP.NET MVC 2. While not technically a feature of the IDE itself, the overall package offers a seamless experience when working with MVC projects. They were made for each other, almost literally.