If they would just bring back current md5 hashes for current builds (whether in forums or more preferably in the downloads section) This would make verifying your current build real easy. Even though blizzard's online store forces you to use a downloader that most likely parses a crc or md5 type hash, they provide the current md5 hash for the games downloadable in their online store in your account page. Anyone who is in the business of online delivery of huge files obtainable without secondary software should do this - its an industry paradigm.
Edit:
Well I checked blizzard and couldn't find md5 hashes - could have sworn they had them at least at one point. But they aren't rolling out frequent builds of the stuff they sell there and people without blizzard's games know when their patches come out.
In GOG's case their files are obtainable through browser and going through frequent builds therefore they really need to post those current hashes.

I have never bothered verifying anything I have downloaded against md5s, a better solution would be to just display what version you downloaded last, makes it heaps easier to check than to do md5 (or just make an optional download/update program)

now a real nice thing would be if the games was mac compatible (running games in vmware is not ideal although it is better since they released version 2)

I'd love to see some console games onhere too, good ol sega & nintendo roms for example, the ability to legally aquire rom images would be cool, especially if those came in the classical rom formats that make them playable on just about anything.

I agree the setup should reflect the version number but that version number won't verify the integrity of the contents. Maybe not everyone wants to install everything they buy right away and as it stands you currently have to do that with the new setups and the lack of md5 posted to verify the contents. I'm honestly less inclined to buy stuff I'm not going to play right away now.
The point is - its effortless to do and could be automated - helps bandwidth challenged - saves money on bandwidth - saves time troubleshooting.
Just because you haven't used a technology doesn't make it not relevant. Source code repositories - server technologies - many aspects of computer science use a similar ideology to verify contents of delivery. CRC in the form of *.sfv files is another example that's been around forever - and still very relevant.
I could throw security in there as well as a good excuse.
Also since the games are DRM and/or "Fingerprint" absent, this is the perfect way to prove to the community that you have the same file as the next guy.

I would like mac games, a lot of the games you're offering are also available for mac, yet you only offer the windows versions.

It is easier as a mac user to use to play older games. Since the games GOG offers are older classics most should work fairly easy this way. Check the [url=http://appdb.winehq.org/]Wine App Database when in question of a game's compatibility under Wine.

I apologise if this has come up before, but game demos available on GOG.com would be a brilliant way of trialling games where possible.
I just found the demo for Sacrifice and tried it out, proving in the process that I could make the game work on my machine. Instant purchase!
- The Unshaven.

I would personally like VERY MUCH to have a forum that works as forums usually do. I'll mention a few points:
1. The ability to use BBCode.
2. For each thread, there should be both a timestamp of the latest post, as well as the name of the poster.
3. Clicking on a thread should take you to the first page, not the last.
4. In a multi-page thread, there should be "next" and "previous" links.
Why not use one of the common (and free) pieces of forum software out there?

in witch case they should provide an install file with wine integrated, much like eve-online is providing an install file based on cider.

I'd like a subscription option..x/month or x/year. This way, we could try the games and not feel like we just wasted money on a game that we wont enjoy. Maybe limiting it to x games/month?

I second that! In fact, why not just make the list sortable? If we could sort it by "timestamp added", "game title" and "number of votes", that'd be brilliant. And very easy to implement.

I would really like to know if the games are single-player only or if they have a multiplayer part.

This may have been mentioned:
For the community forums:
- a quick reply
- quick reply and normal reply should not launch a separate window
- it's annoying for one
- some people may be browsing from a work computer and may not be able to reply since usually those systems have browsers that block every pop-up.