It's well known that while Moose competes well with hand written code at runtime. However, Moose code still needs to pay a lot at compile time, due to the comprehensive extensibility of the metamodel. We've previously made fairly successful attempts to optimize startup but there's always room for improvement.
Thankfully Goro Fuji has received sponsorship to optimize Moose's startup time, and even though he only started working recently his efforts are already paying off. I expect to see many exciting developments by the time August is through!
Ongoing performance improvement projects have been slow going due to their difficult nature, and lack of volunteer time. Because of this I am very pleased to have such a talented programmer working towards solving this problem.
If you would like to see possible improvements to your Moose based code's startup time, please consider contributing NYTProf profiles, so that we can more easily identify the slow path for real world scenarios. Different apps have different needs, and the more data we have the clearer the picture gets.