The 3D modeling section of SYSmark is fastest on a non-encrypted partition.
The video creation test that utilizes Sony Vegas 7.0 and Adobe After Effects shows benefits from the quad-core Core i5-750, but the dual-core processor also does well, probably also because of AES support in BitLocker. Overall, TrueCrypt is still slower in this test.
There are few differences in the productivity test. Again, an uncompressed system partition provides the best performance, but the delta is small.