Nah not really. I've had a few emails sent to and from Trifecta, and decided that I might as well get the Powerchip tune. I am sure that eventually either VCM will bring one out or Trifecta will find a reseller (maybe someone like Walkinshaw as you say), but it will be a long while before that happens. In the meantime this IS available and it's a fair enough result, so why not.
As for warranty, yes it does affect it. The main reason I have decided to go ahead with it so quickly and regardless of whether or not it affects Holden warranty, is because Powerchip offers 3 year warranty on their programming (PowerchipGold98). Meaning, that if any damage results from their program to your engine, it IS covered by them. This came out of their mouth "if we were to install the program and you find it that your engine blows or whatever, we will buy you a new engine". The rest of the warranty is unaffected (i.e body, suspension, exhaust, etc.etc.) SO all in all, you're covered. It can be removed if you wish so at a later point as well, but apaprently there isn't even a need as the chances of it being picked up by "tech2" are next to none.