I tested LD Video Essentials with bunch of cards including ATI 750 HD PCIe.
Other devices I have used:
Compro VideoMate TV Ultra, ATI 550 Theater PCI, Panasonic DMR-ES25 as path-through to ATI 600 USB and ATI 750 HD PCIe.
I have used Pioneer Elite LD-S2.
Unfortunately ATI 750 HD PCIe triggered AGC problem. This same problem was triggered also by ATI 750 HD USB when I used S-Video out from LD-S2.
As far as comb filter goes 750 performed the best from DVD test captures. However, on LD VE capture it didn't do as good job perhaps due to the LD noise. IMO, the best comb filter for LD capture was NEC D64083 which is inside Compro VideoMate TV Ultra. However, the entire image is much blurrier than that on ATI cards. I can post images and/or mpeg samples later.