These days, many projects have started their life written in Java. Some of them are eventually converted to C# for incorporation in .NET. Examples that come to mind are log4net, nhibernate and db4o.
Including sharpen (which is db4o's tool) have you seen and/or used any tools that make continual conversion manageable. I'd go so far as to say anything that requires more than about a 2 month slip from the original product release isn't really all that useful for continual conversion.