There is no problem to precompile Sitefinity project but it will not help much since there is very little dynamically compiled code unless you have custom modules and user controls.
If you have custom modules, you can speed up the startup time a bit by removing the automatic database upgrade in the static contractor of your WebModule class. This way the database schema will not be compared and you will have to run the upgrade manually when you make changes to your dbclasses or static queries.
Note that most of the time on startup is taken by the JIT compiler and initialization processes. Precompiling a web site does not affect the JIT compilation.
All the best,
the Telerik team