With microsoft.net technology and windows forms 2.0 you can build great application. It provides great user interface component so you can develope very reach applications.
There are two aspects of application design and another one is performance. If any of this two is not perfect then your application may lead to a failure.
I have found one interesting link that discuss about this issues. It discuss all aspects realted to design and performance. It discuss about common performance-critical scenarios such as startup, control population, and control painting to boost your application performance and make it user responsive.
here is the link: