I'm currently developing an "technical" application in .NET, and in short: .NET is OK idea, but.. I'll try to avoid it in the future.

Positive things:
- multilingual (Managed c++, C#, VB.NET)
- totally integrated in Visual Studio
- documentation
- bunch of controls (free and non-free)

Negative:
- managed c++
- deployment
- events (i prefer signal-slot functionality)
- cross platform NOT

It has nice things like it's own types (Double instead of double, Int32 instead of int, etc..), logically named and categorized classes..
Biggest negative thing is that you are doomed to managed c++ if you use .NET Framework.

My opinion is that Qt has a brighter future.

Currently, use Qt 4.5 and VS 2008 with Qt Visual Studio integration. And in near future maybe Qt Creator will be able to substitute VS. We all hope