Yes, it is a fact. Also, anyone you ask who knows what they are talking about will advise you NOT to ever attempt to upgrade a project to .NET. It isn't worth it.
For small-scale applications, you should rewrite. For large-scale applications, you should keep them as they are.
It just isn't worth the hassle of having the upgrade wizard generate non-standard .net code (which it does) and having to track down potential bugs caused by this.
I have heard the upgrade wizard is significantly improved in the next version of Visual Studio .NET, however. Not that I believe it will be worth converting even then, but it might cope with your usercontrols better anyway :)