From a development (coding) standpoint I have worked with both as a Java developer and a C# developer (connecting to both on various projects, so Java to SQLServer, Java to MySQL, C# to MySQL, C# to SQLServer). Personally I didn't really notice that much of a difference although I wasn't doing anything too complex. I don't think there's too much to worry about if you're thinking there will be a steep learning curve unless you want to get into some of real nitty gritty server specific stuff. There are some minor differences, but nothing that someone wouldn't pick up on quickly.
