Probably not applicable right now during the beta, but in the future will there be sales and bundles? Like for instance - a weekly 10% off deal like with steam? Or, using Earthworm Jim as an example, a deal if you buy every game in a series together?
It's so much easier to justify spending money when you know you are getting a good deal. Mind you, with these prices it's not like it's breaking the bank anyway. :D Just a friendly suggestion.

I think 6$ is already a great deal for most of the games in the catalogue...

The price is right... no doubt... but I might be more inclined to purchase more if say you offered buy 3, get 1 free type of deal on occasion.... pretty common sales gimick that is used frequently in the business world for good reason.... it works!!

No argument there, I was thinking more along the lines of larger purchases - like 3 or 4 games worth.

If they had a deal like that I'd probably end up with every title they have available currently.

I'd like to see a deal where you can get an entire publishers catalogue (once there are more publishers and more games) for a combined price that's worth maybe a few games off.

I just bought the rockstar collection off steam for a VERY low price, so yeah I'd have to agree.

It's already cheap, and you can add them to a cart for a single purchase (Saving on multiple bank charges, if applicable, as this is where the snowball grows). Even 3 or more titles, and it's still very good value.
I would like to see an easy option to add a set of titles to the cart in one go though, either as a series, publisher set or 'suggested best-of back'. But they don't need any further discount.

What I was referring to, was 20 games for maybe the price of 17 or something like that.

I think the games are remarkably cheap as it is, lets not forget some work has been done to make these vista/XP compatible, which in some cases is no mean feat.

Also, people who miss the sale, will usually go 'oh well, full price then.'

I think you're missing my point... People may be inclined to buy games they might otherwise pass on at full price because they are getting a deal... People who really want a game are gonna pay full price anyways because they want the game, but people who "maybe or kinda" want a game will pass on the game at full price (even though its a good deal anyways) but might go for it if they feel they are gettin a deal...

Maybe a medium-long term 'stamp' type loyalty card scheme? Something like each time you buy a game you get a stamp (obviously a record in your profile rather than an actual stamp like a physical store loyalty scheme), and once you have X number of stamps you get a free game. Agree with previous posters though that the prices are already fantastic (even considering the UK Pound's recent fall against the dollar) and the deciding factor for me isn't price but just whether I want the game or not.

I think most everyone here is already aware of how great the prices are that they're getting already. Honestly I would not buy more or fewer games if I got the equivalent of a buck off or something. I just got four games for 20 bucks and I'm ecstatic. The last thing I am caring about is if I get a dollar off one or all of them.
The only thing stopping me from buying more is that there is only so much time in a day; if I got more, I couldn't even play them for a good long while. If I got another game, it would be because the game struck me as so awesome I just couldn't help myself. And I wouldn't care if I paid the tiny "full" price that GOG charges.
I'll be back to buy plenty more games here after I slowly chew through the ones I got. When I do, whether my card gets charged a buck or two less because I got in on a sale won't make any difference to me. GOG is welcome to it.