it gives a couple of suggestions with a link to a knowledge base article on speeding up the RadGridView and also using NGEN to create native images which will help with first time load speed.
This happens because all of the Telerik controls are themed, so it takes longer to load, because it is not just loading the controls, but also applying themes and other visual artifacts.
There are a few ways of improving performance, like disabling all the animation effects in the application (the most drastic one),
For your case i would suggest using a SplashScreen, this one actually looks good, plus you could add your own customizations very easy, like a telerik progress bar, maybe some transparency and it will provide way of letting the users know that the application is starting. (plus, after the first launch it will use the registry to store the previous launch timer required).
Hope this helps, if you have any other questions or comments, please let me know,
I agree with Emanuel that the themes take the time to load along with the animation effects. It's best (if you can) to reduce the number of themes that are loaded also.
I've used this splash screen suggested before and it's certainly one of the better ones, though in my view, the other suggestion made by Emanuel together with performing an NGEN on the executable and dependant assemblies are the route to improving the performance rather than masking the slower load by using a splash screen.
Let us know how you get on with it.
Best regards,
Richard