Just in case you didn't see my response on the Premiere forum...
The HS card was designed as an "OEM" card really...something that could be (relatively) inexpensively bundled with certain software and/or hardware to get HDSDI I/O on a system...
The HS card does NOT have:
HD analog component I/O
SD analog component or composite/YC I/O
Hardware HD to SD downconversion (I use this all the time)
Native support for DPX, Cineon, TGA, TIFF, BMP sequences
2 independent SDI/HD-SDI outputs (The HS card has only 1)
2-channel balanced XLR analog audio I/O
RS-422 machine control
AJA Machina software
For the money, I think the LH/LHe cards are a better return on investment for a general-purpose editing suite that may switch back and forth between SD/HD...uncompressed/compressed, etc...
In a very narrow application where you knew you'd always only need digital HD I/O...the HS would probably be fine.
Really if you are going to be using After Effects primarily and all HD-SDI you should choose between the HS and the XENA 2K or 2Ke. These cards will give you the highest framerates of RAM preview output.
Also the XENA HS is PCI-X only, so if you are looking for a PCI-Express, you should probably opt for the 2Ke.