My experiences are similar.
Last week I bought a D630. (T7500, Nvidia 1280x800, 4GB RAM)
I changed Wifi to a Broadcom BCM 4311.
I installed 10.8 exactly according to the EDP manual, and the whole system was slow, not only the graphics.
After using the tips of "Performance Tuning with FakeSMC" everything is much better.
Maybe EDP should be adjusted for the D630 Nvidia model.