Will there be a Linux client download for TW2 on GOG.com? Or is it only a Steam OS thing?

GOG staff did announce that Linux support is coming eventually, so definitely.

Considering how they didn't want to introduce Linux support because of possible trouble with ports and the fact that currently Witcher 2 works only on nVidia cards, I think it might take a while to get there.

People are not too thrilled about the performance of the port... so... better that it appears on here at a later time, when issues are sorted out

That being the case I'd be happy to wait until it appears in GoG, although it would be nice to see something official from GoG, i.e. a 'coming soon.....' or the like.

Personally I'm pleased to see Steam support Linux / Steam OS (Valves customised Debian GNU/Linux). I believe it's great for gaming, obviously great for Linux.

Well, it's not a Linux port. It's just a little better re-packaged version of TW2 with WINE.
Don't expect similar performance compared to the native windows or mac clients.

Actually it's not Wine at all, it's a proprietary piece of software called eON from Virtual Programming (VP). Reports are that the windows version, run with wine (and possible the CSMT patch), is actually better and faster. Not by a lot but enough to make it more enjoyable than the actual *ahem* port. This is my experience as well.

Friday is a bad time to release anything... Two days without support people on the job is cray-cray

The following is just me pondering on eON:

The developer that took to the Steam forums said that eON is something between togl and wine and that it is also "targeted" at the game that it's being used on. This is confusing to me since togl is just a D3D to OpenGL translator and is only part of the final product that, in this case, are Valve's own games. Yes they translate D3D to OpenGL but they also ported the entire code base. So what you get is native executables.

VP pride themselves on the fact that they do not need access to the source code in order to create the ports. You know what this sounds like? Wine. It has to do it like wine since you're not running native code, you're translating Windows API calls to Linux.

Two things also stood out to me:
1) they say that, unlike wine which has the goal to eventually be as feature complete as possible, they're customizing eON for each specific title. So, not only is eON a proprietary blackbox but also less feature complete and less mature, tired and tested than Wine.

2) they say that, on this occasion they had to re-write to shaders to GLSL. So it's not like simply slapping wine on there. Correct, but companies like CodeWeavers also do targeted builds of wine (which may or may not contain stuff that can later be included in Wine. The project won't accept kludges that work only for certain applications) and they also will re-write shaders if it needs to be done.

Link that shows all his posts on the matter:

http://steamcommunity.com/id/jaycee1980/posthistory/?p=1