Oh brother. No, you don't have to throw out your old applications IF YOU DON'T UPGRADE THEM TO VB.NET! And yes, if you write your new applications from scratch, then VB.Net is fine.
But if you aren't upgrading your old applications, and if you have to move your team to a new environment for your new "from scratch" development, there are other alternatives to VB.Net (e.g. C++ and Java, among others).
What VB.Net fails to do is make a compelling case to "upgrade." That's why it has grown so much more slowly (especially compared to its full potential) than VB 6 did in original corporate acceptance.
I guess we all have our opinions, mine is .NET seperates the men from the boys some. Just like a lot of the bandwagon NT domain admins can't handle Active Directory. You can still run NT, or VB, you just can't get free support anymore. See ya round.
First, Windows. Now, VB. Dude, you're wasting your time. Stop crying and go open source. You'll be happier. Commercial companies don't have an obligation to hand over their intellectual property.