I have had Llumar (offered from Quill) on my 3er and I can immediate tell everyone to avoid it. Its heat rejection is much inferior to the trusted Vkool elite on my wifey's cars (current and previous rides).
As for my new 5er, I feel that the factory windscreen must have some sort of heat rejection capability too, it wasn't hot at all under 35C compare to my previous 3er even with the Llumar installed. So, I would probably go back to Vkool Elite ..