I have used several Thinkpads built by IBM for about 15 years. They are excellent and have no compatibility issue with projectors. Don't know the quality of the Thinkpads built by Lenovo. Laptops built by HP seem to be good also. I heard several negative experiences from Japanese people using the Sony Vaio. I would stay away from the Vaio if you intend to use your laptop for presentation. There are compatibility issues due to softwares that Sony added to the system.
Dell Precision line.
I have to respectfully disagree...I deploy both Latitudes and Precisions at work and prefer the L...better build quality...the XPS line seem quite nice but I have no hands-on experience there...
Cheers.
-J.-