A couple of days ago at work, Fred found this great tool for editing MSBuild project files, it’s called MSBuild Sidekick from Attrice Corporation. It works pretty good, although there are some quirky things with the UI (mostly with the way the treeview behaves).
The tool does make it a lot easier to change a project file because it gives a graphical representation of the MSBuild tasks (the less you have to remember the schema, the better).
If you’re doing some work with MSBuild, you should check out the tool. It will be worth your time.