When I looked at beta 1 of J#, I found so many bugs in the first day of playing with it, that I decided to report the bugs to Microsoft and then ignore the product until the next beta. When beta 2 arrived, two of bugs I reported hadn't been fixed, but I decided to go ahead and play with it for a couple of days anyways. What I found was devastating: The J# object model is fundamentally broken. In order for it to function, it requires a huge security hole. I reported this to Microsoft and gave up on the tool. Since then I've been looking for an alternative, but recently I finally decided to build my own JVM for .NET.