I'm new to GOG but I'm considering pre-ordering a copy of W3 on GOG instead of my usual route thru Steam.
I'm considering this because I want to support CD PR even tho it's slightly cheaper on Steam for me.
What I'd like to know is, will I just access W3 from a desktop icon, as with non platform games?
Will I have to access it via my GOG account? If so, is that usually easy and problem free? Do you anticipate much of a W3 community on GOG? I'd appreciate your feedback, thanks.

You use GoG only to download the game.

You install it and run it WITHOUT a client, or need to be online. You can even back it up on DVDs.

Forget all that steam thing. No one limits you here on anything. You download once, you keep forever without restrictions.

If you own Witcher 1 and 2 on steam, redeem their code here for a free GOG COPY of them both. This will also earn you a discount in preordering 3.

You can access it via a desktop icon yes. You have access to the files to download via the account yes. It is usually problem free yes - suggest you grab the free games and test for yourself.

There is a client named Galaxy in the works, it will be more of a steam like hub for your GOG account. It is optional and WIP.

Even in the general forum threads around the Witcher pop up from time to time. There is a dedicated forum I'm sure, and I expect it to be one of the more active ones, suggest you go to it and check for yourself. As for modding community, if that's what you mean, I can't speak from experience.

In case you haven't done so already I suggest you try one of the free games that you can get here on GOG.

Choose one of those games (Beneath a Steel Sky, Lure of the Temptress, etc) download and install it. The procedure is exactly the same for all GOG games.

I'd recommend Tyrian... Loved that game...

On GOG everything is optional. You may even take your game with you and never come back if you wish.
Profile, achievements, updates, game tracking.. it is all up to you.

and welcome aboard!

Yes, do that, this will net you a 10% discount on W3 ;)

At the moment, the main difference will be that gOg do not have a client yet (it is in alpha), which means you need to manage the game yourself (manually download and apply patches and so on), and there are no working achievements and other meta-game thingymabobs. If you do not mind the above, there is next to no difference between the gOg and Steam version of W3.

This is a free State at Gog,no catches,no gimmicks,all good.

The CDPR boards are more likely to be. Know that your gog account and cdpr are linked in some way I believe.

Welcome to GOG. Honestly, you'd have less of an issue here than elsewhere. I like GOG because their approach ultimately means I'll have less of a hassle in accessing the games I buy (at least compared to other clients/DRM schemes that I have used in the past). You will not have to worry about buying the Witcher 3 here :)

Once again, welcome!

With GOG you're buying a game. With Steam you're buying a service. Take your pick. Experience and mileage will vary.

Welcome to GOG :)

Welcome to the online EB Games equivalent there's your difference. The Steam platform itself is DRM most popular games on it exist in the cloud, some come with hidden DRM, while others don't even make use of any of the Steam specific features. However all games on Steam require Steam to be running in the background regardless if its online or offline. If Steam ever goes down as a service you could theoretically lose all your bought games.

On GOG "YOU" the user own your purchases, it is not locked to an internet db or repo and best of all GOG has a DRM free policy. Steam has lost its shine over the years, most games on Steam these days come from Kickstarter. Most indie game designers release for Steam because they want popularity rather than selling quality. Some games that started out on Steam have even made it to GOG. Some have an agenda others simply want to cash out of the Steam platform.

I'm surprised people still need to know these things in 2015!!

Without Galaxy you hit up the site, login, go to your shelf, download the installer. Run the installer and then you just launch from a shortcut or whatever.

That said, Galaxy is coming soon and that works a bit like Steam. You go to your library in the client and click install and then can just launch your game from there. Patches and updating and such is handled by the client just like in Steam. You can look on YouTube for videos of people in the alpha.