I see dozens of interesting games here but reviews, pics and videos only tell so much.

Anyone else who would like to try these games?

Demos that work on modern computers would be awesome but probably more work than whoever would be in charge of that is willing to do. I tried playing demos for Outcast and Divine Divinity and neither work on my computer.

No point in demos because internet is full of quality reviews, gaming videos and so on that surely give you enough idea if the game worth of buying.

I never use demo's, since I'm filthy rich I just buy whatever I want.
But seriously, I doubt GOG will want to spend even more time on a game then they do now to create a demo. Their profit margin is probably already very slim and to spend even more money to create a demo is probably just not very economically viable.
Personally I don't care since I really don't use demo's, I read some reviews and check some footage and screenshots and then decide. Maybe I'll like it, maybe I won't but worst case scenario I'm out $9.99.. I can live with that.

And alone that's nothing but when I see 10 or 50 interesting games the total price would be BIG

I don't know how much trouble it is to create a demo but I imagine that once the game itself works it isn't too complicated to cut it down into a demo or add a timer.

There is a thread containing demos for a lot of games here.
It's not updated too much now, but still it's good source. And you can contribute yourself with more games. ;-)
Link

It's quite easy to find demos with Google and I'm doing it now. I was just thinking it would be a nice feature here. Not something absolutely needed though

It is extremely complicated if you are not the one who made the game and don't even have the source code.

wasnt there already a thread with a lot of links for demo versions of games available here?

edit: nevermind, just noticed that it was posted here

Should also remember that some demos will install some nasty DRM which may not be uninstalled with the demo . . . just saying . . . =)

I hit up fileplanet.com for my pc game demos. Like another poster said though, they sometimes don't work for whatever reason. But I've probably been able to try out 85-90% of the games I've been interested in before buying. It would be handy-dandy if the demos were right here on GOG--would've probably aided in getting twitch buys from me--but most of the digital pc game sites are very lacking in demos. But check out fileplanet. For instance I was able to demo the AOW games sans Shadow Magic, Arcanum, Divine Divinity, Baldur's Gate 2, Fallout Tactics, Fantasy Wars, Gothic 1 &2, etc. If the demo isn't on there, there's a high probability that the demo simply doesn't exist. Happy gaming.

Old demos for these games have several flaws:

1) They contain nasty DRM, often, in fact, as Stuff said.

2) They often are unpatched, the GOG version will be either the latest version or the "best" version as the community agrees (e.g. Temple of Elemental Evil is at the patch level that supports several very popular mods).

3) The GOG version often includes any expansion files and other modifications to the game executable.

So basically, if the demo won't run on your comp will the game? You can't know very well with old demos. If you just want to know what gameplay is like read reviews and watch videos on Youtube.