We did some performance tests for this scenario and they confirmed it very clearly. We were able to quickly find the bottleneck and to eliminate it. The optimization reduced the initialization time in half. It will be included in the service pack that is due in just a few days.
You should also set <compilation debug="false" /> in web.config, if you have not done so already.
Thank you for bringing this issue to our attention. Your Telerik points have been updated for your involvement.
All the best,
the Telerik team