There is no tool/wizard intelligent enough to take advantage of OOPs, Multithreading, Ado.Net and other features of .NET.
You will have to do lot of manual work before migrating any VB6 application to .Net, if you want to take real advantage of moving it to .Net.
If you blindly move it .Net using Wizards, then be ready to maintain it, no good developer would like to work/maintain on such a junk code.
My own Strategy to Migrate VB6 Applications to VB.Net. (It takes time, but worth)
Step 1: Use Code advisor for Visual Basic 6 from microsoft, to do Pre-Migration changes (VB 6 Code Cleanup) (Manual/Automation)
Step 2: Decouple the presentation and business logic (There are lot of VB6 applications in which business logic is merged with presentation logic, in the form of event code). (Manual)
Step 3: Change your VB6 application, so that it will easy to use Micosoft Application Blocks (Manual)
Step 4: Migrate VB6 code to VB.Net using Microsoft Upgrade Wizard. (Automation)
Step 5: Do the code analysis to use Microsoft Application Blocks. (Manual)
Step 6: Try to use ADO.Net/Multithreading where ever possible. (It will definatly shootup application performance) (Manual)
Step 7: After complete migration, you need rigourous testing, your business logic may change because of datatypes (variants/objects). (Manual)