"TEK players have happily reported that thanks to the latest Viewfinder upgrade 1.52, the game is now running very well with this special graphics card. TEK is displayed without any optical problems. Thus, Viewfinder users can now safely buy TEK, and TEK players can safely buy the Viewfinder card!", Jan informs us.
However, Windfall's Viewfinder support page details that Version 1.50 was the last free upgrade to the software. V1.53 is actually the latest version, and is avaliable to download from the site - but you do need to pay 20 Euro.
No sign of the promised TEK Demo yet, although people are probably too happy about the recent Pyro updates to care too much.
Source: Artex Software