I am an iOS developer just getting started with Windows Phone.  At the moment, I have the free product Visual Studio 2010 Express for Windows Phone.  I see that Microsoft has several higher-end IDEs, and some of them have some very fancy price tags.  My question is -- will upgrading get me significant advantages?One thing I find very annoying is that unlike with Xcode, Visual Studio Express does not let me edit my source code while my app is running.  (I don't need fix and continue; but it sure would be nice to be able to make changes while it is running, and have those changes applied the next time I run my app.) 
Windows 7 Phone -- what version of Visual Studio to use?
windows phone 7
For a full breakdown of the features of each version of Visual Studio 2010, you'll want to see this.The only major bonus that I know of for moving from Express to any of the other editions is VS add-ins (or TFS integration, which I suspect isn't a talking point for your situation).When you get to Premium and Ultimate, you get the testing and lab management features respectively - which can be handy, but there's lots of 3rd party stuff that can successfully fill those roles (most of which can be free). There's also the diagramming features, but I don't know of anyone who actually uses them for much.Specific to your mention of editing source while running, IIRC the debugging features are the same across the editions and I only recall there being specific instances where you can't do that.