On the main page, there is a banner about gaining xp and a "check your progress" button. There you can see how much xp you have and how much you need for the three games that you can get. After reaching a xp threshold you get a code you can redeem to add the game to your library.

The XP is only worth anything for unlocking the three free games listed on the "My Promo Status" page: Expeditions: Conquistador, Dex and Victor Vran. Those are automatically added to your account upon reaching the required XP, except if you already had them, in which case they turn into gift codes.

So I'm restricted to only picking those games even though games on sale like the witcher 2 cost xp?

The xp you see for Witcher 2 is what you get towards those three when you buy Witcher 2.

They don't "cost" XP. They give XP toward gaining those three freebies, at a rate mostly equivalent to 1,000 XP for every $ you spend. And that promo page shows you how much XP you've gathered. (And yeah, your selection is limited to just those three games, of which the cheapest one can be got by anyone without spending any money at all; last sale worked exactly the same, with a selection of three different games.)

Also, you don't actually "spend" the XP you earned. So getting Expeditions: Conquistador and Dex won't make it more costly to get Victor Vran. The XP just unlocks them once it reaches the right level.

Therefore they restrict me to only picking one of those three games under the "EARN XP TO UNLOCK THESE GAMES" banner? That's unfortunate.

Exactly.

Yes you only get free copies of the games the banner clearly tells you are the only three you can earn free copies of.

XP system does not seem like an alluring deal. I was allured, because it looked like after buying a lotta games and earning tons of XP I would get a discount towards more games. BUT that is NOT what XP turns out to be. Turns out, you earn tons of XP and then they unlock a choice of 3 games. So I thought, OK I get ONE FREE (I had spenta LOT of money clearing out my massive wishlist backlog, and then figured I would buy the last bunch of wishlist games that cost more, by using whatever discount I earned in points towards getting those. So my zillion games purchased games gave me a choice of unlocking 1-3 certain games, 2 of which not my taste (horror and shooter) as I am a rpg and adventure type mostly with a smattering of rts. So I picked Shadowrun Dragonfall director's cut, which is a good rpg. (I already own Shadowrun on android, but tablet's broken and anyway, pc versions are nice to have. I have never gotten any of that series on pc). Shadowrun unlocked. OK good. Then I chose and bought another 10 games for another (including a couple I've been waiting a year to get that were not on sale) and afterwards looked at the tab. WAIT - Shadowrun showed among my purchases at a charge of $3.99. HUH??? After all that huge buying, not even ONE free game??
Not such a good deal.
Even now, after buying my wishlist (or most of it) and using XP, the site tells me "You've gathered: 564690 XP" - so it's NOT that I didn't earn enough XP or buy a sh--load of games. I have been a gog customer for a LONG time and love the winter sale.
I'd have bought fewer games all at once, if I understood that XP doesn't mean much. DUH!

SO, THIS XP THING IS NOT MUCH. PLEASE TWEAK IT BETTER. Maybe consider, for the big annual sale, a sliding discount scale based upon dollars purchased and number of games bought during that sale event? And maybe look over your XP explanation to see if it can be made really clear, for gaming customers who are laboring bleary-eyed at 4am over their huge wishlist during the big sale, instead of sleeping sensibly and not buying luxuries. (However well-priced, they add up when one loves well-crafted games as preferred entertainment). For all you guys that are laughing that I fell for the XP thing.

I love GOG.com and recommend it to EVERYONE. And whether I earn freebies or discounts for buying lots of games, I STILL prefer GOG. Because I DISLIKE STEAM's whole DRM & forced resident client thing (I like to control my own PC thank you), and forced DRM online check-ins, and so I have resisted using Steam. Even after they changed their unresponsiveness and no-refund-ever policy, I still refuse to use Steam. Don't like how they play in the games distribution industry either, trying to lock out other distributors. I wait LONGER for games just to avoid using Steam. GoG has had better security for customers, too. I like your business model. I like that you have a good forum for info on each game; that you have lots of the types of games I enjoy, and I love your easy download, updates, etc which are clean and simple. And I dislike subscription models since I like to OWN games forever, because they are works of art and entertainment, and because it's criminal when beautiful games are forever shuttered as with so many mmo's... I prefer offline gaming.

Lack of sleep is a terrible thing. At least that's my excuse. Which doesn't hold water, since the last month I've lost a lot of sleep to Skyrim, grinding for better gear to beat the bad guys. But it's much better than hanging out buying drinks, or hitting up "Black Friday" all night shopping or bookstore sales. The only problem is my HUGE backlog of owned games not yet played.... Which is a lovely problem, indeed.