I have used both and much prefer Visual Studio. The reason I tried SharpDevelop was because the Express editions of VS didn't allow for Window Service projects. Since you own a software company, you should check out BizSpark from Microsoft. They give you VS 2010 Ultimate along with a whole lot of other useful stuff (such as MSDN subscription).
Personally, I was able to get VS 2010 Professional because I'm enrolled in school (so far one of the best things about my MSCS program :) ). I don't know if I could do anything .Net related in anything BUT Visual Studio!
Here are reasons why I like VS over SharpDevelop (after all, it helps to answer the OP's question huh?:))
- VS is more aesthetically pleasing
- I knew VS from the express editions, so it is one less thing to learn
- I felt SharpDevelop was slower than VS and I didn't like it
- SharpDevelop couldn't handle F# (when I tried it, it was a mess). VS Shell and F# worked for me though.
- VS Shell allows for other language support (IronPython, IronRuby, etc.)
The benefits of SharpDevelop
- It allows you to do projects that VS Express Editions don't. For example: windows service
- It is free...completely
- It has a bunch of other language support built in
If I wasn't able to get a free version of VS 2010 Pro, I may have eventually switched over to SharpDevelop, but chances are I would've stuck with the Express editions and used workarounds to do what I needed (such as using Entity Framework in Visual Web Developer and then creating a library and importing it into Visual C# Express)