I do have several of VGA / DVI capture ones,....

Matrox MXO, only works for MACs
Canopus

Most of them converts the signal to VIDEO, even to HD Video, still Video....
and is not good enouth for PPT presentations or so, only for big logos or caracteres.

Epiphan is the best quality so far, specialy because is what they call Frame Grabber... But yes the Drivers have some conflict with Catalyst. He only works if catalyst has the Input from Epiphan,... if not catalyst crashes.
So we are on a painfull job to unistall the driver when we use Catalyst without the Epiphan, and install the driver when we use the Epiphan, and open Cat only when we know for shure the Signal is coming in.

But is great quality, specially if you compare with other products.