In addition to Bill's very valid remarks, you have to keep in mind that to gain from HDMI's output, you need at least 200 MB/s sustained transfer rate which is not possible on a laptop.

HDMI is a poor man's substitute for HD-SDI

That is not true at all. There are many formats that you can capture to that are not as large as uncompressed. On the Apple side there is Prores and on the PC side I believe the Matrox products will capture I frame only mpeg2 based video up to 300 mbits/s (bits not bytes) into a AVI wrapper. Sure it isn't uncompressed but some of these formats can beat the pants off of even HDCAM and offer an excellent trade off between ultra high quality and manageable datarates. I always see people instantly assume a HD-SDI, SDI or HDMI capture device has to capture uncompressed and that is just not true at all.

You can use AJA Io Express:
Io Express - AJA Video - Serial Digital Video Interface and Conversion