I heard many complains about slow startups of mobile applications and also got questions how to increase the startup performance. In most of the projects, the problem was a design issue, just like trying to connect a remote server on startup or populating big datasets etc.. But on the other hand, if you think your startup sequance is totaly clear and correct than you may find some more things to do in general.
Take a look at the article on how to optimize the your application's loading time.
http://blogs.msdn.com/raffael/archive/2009/01/05/netcf-improve-startup-performances.aspx