Since I'm NOT a developer of the project, I figured I'd chime in also. I've been using SharpSevelop since version 1.1, and it was my first dive into .NET development. I saw that to get some of the capabilities I wanted with Visual Studio, I'd need the Professional version priced at around $1,000. Since I mostly work on smaller projects for Rent-A-Coder, it would have taken too long to break even, so I didn't get into .NET for a while.
Once I discovered SD, I figured it could at least get me started, but I haven't looked back since - it has proven itself to be worth every penny that I would have spent on Visual Studio. I've since used it on a few rather large projects, and where I once was hesitant to tell clients I used it instead of Visual Studio, now I'm completely comfortable with it.