Posted a guide about how I got it up and running here: http://www.neant.ro/2011/12/planescapetorment-on-linux/

It runs in fullscreen, I can change desktops, alt+tab out of it without crashing, edge scrolling works and I have no artefacts on screen. Basically it's just like on Windows so far, it even crashes sometimes on area load, just like on Windows. I played a little bit, didn't get to test the whole game yet. My initial idea was to repost the whole thing here, but it took me too long to get to this point and right now I've kinda had it. Maybe later, though probably not :). I hope linking to my site is all right.

Anyway, the short of it is this: I'm using wine 1.3.27 on Debian, Gnome 2 + Compiz, NVidia card with the NVidia driver from Debian's repo. Install wine, use default settings, except set DirectDrawRenderer (ddr) to opengl and OffscreenRenderingMode (orm) to backbuffer. This can be done easily with winetricks. The orm thing gets rid of (most of) the graphical glitches the mouse cursor leaves behind. The game should start and work fine now, but sometimes characters have graphical artefacts around them. Turn on Software Mirroring in Video Options to get rid of those too. Hopefully it works, so enjoy. More detailed instructions on site.

I really hope this helps someone, it took me days, literally, to get here, didn't find the orm setting posted anywhere else and that's what made all the difference for me.

Thanks for the howto, works perfectly on linux mint 14 with play on linux.
Gives an error at the end of the install though, but doesn't seem to impact the game.
Had the mousecursor bugs, but after correctly setting wine options it rruns great! (didn't neet to set the software rendering bit inside the game)

I would not recommend using this guide. Not only is it 2 years old, but even 2 years ago, there would have been some problems with it. For example, The "DirectDraw fix" is for Windows ONLY. The "DirectDraw fix" is needed for Windows Vista and up, because MS depreciated and broke compatibility with their own DirectDraw in the newer versions of Windows. Ironically, the "DirectDraw fix" uses parts of wine, compiled for Windows, to translate the DirectDraw calls to openGL. Not only would it be redundant on Linux, since you are already using wine, but it will most likely cause problems.

The best advice I can give you for running any GOG game on Linux, is to use PlayOnLinux. It has support and install scripts for almost all of the games on GOG.

As far as the mods for PST (and any other Infinity engine game), you can run the Windows versions of the WeiDu mods from a wine cmd prompt, which you can open up directly from inside of PlayOnLinux, under the "Configure" tab. I believe the "Linux" versions of the WeiDu mods are intended for the gemRB engine and the Linux WeiDu installer. While you could use them, all of the mods should be installable through a wine cmd prompt using the Windows versions. The only difference between them are that the Linux versions are all lowercase files and lack the installer. Wine however, doesn't care about the case sensitivity. I have also had some major problems with certain games with the Linux WeiDu versions and I have had absolutely no problems running the Windows versions through wine. The Linux versions would probably be necessary with the gemRB engine, however, they are not necessary with the original Infinity engine through wine (and you will in fact probably have less problems installing them through wine, not to mention it being easier).

Lastly, wine version 1.3.xx is really old and I believe it was old 2 years ago. Newer versions of wine should be able to run PST flawlessly, along with all of the WeiDu mods (I have been running it with wine version 1.5.16, along with all of my other GOG games) but installing your games through PlayOnLinux will allow you to use different wine versions if needed and sets up and handles your wineprefixes automatically in the background. One of the first things the PlayOnLinux install scripts does (GOG version) is remove the Windows only "DirectDraw fix" automatically, in the background, so you won't have to worry about that either. You will also get a shortcut with the original icon to run it, (with all of the prefix settings taken care of automatically in the background as well). It is a lot better/easier method of installing, running and managing your games on Linux.

If you are a new user, PlayOnLinux is really a must have, but it is still a blessing even for an experienced user.

hehe you're right, it's very old. I did use play on linux and it installed the gog executable, but i still had graphical corrution issues.
the "Short version: in Wine set direct draw renderer to opengl, offscreen rendering mode to backbuffer" from the guide was really helpful from the guide in that regard, works perfectly now!
If i don't set those options my mouse cursor leaves all kind of corrupt trash all over the screen.

Anyway, i've been playing the game for a while now, but didn't check the modding part. Going to try your tips ASAP, thanks... it really looks weird on a widescreen laptop :)