I have been running APEX 2800 v2 cards and it doesn't seem to matter. Can I get your Teradici/Vmware ticket numbers so I can reference them? I am having a hard time proving it to VMware as it is subtle and they are now telling me that the K1 cards are only supported with ESXi 5.1 U1 which ironically causes the APEX 2800 cards to cease to work.
I played around with that PCoIP tool in the above post and got interesting results. I was playing a 1080p Star Trek movie trailer in VLC. Both hosts are identicle aside from the K1 card and both have APEX 2800 v2 cards.
-With build-to-lossless enabled total max B/W was 35Mb/s, with K1 card was jumpy and without K1 card was less jumpy (though still slighly jumpy on panning frames)
-With build-to-lossless disabled, with K1 card was now very smooth with a total max B/W of 10Mb/s and without the K1 card became jumpy with a total max B/W of 4Mb/s
With build-to-lossless disabled the GPU was also running about 5% more utilization