I posted this on our game's subforum as well, but I thought it would be of general interest to the GOG community.
A big question everyone has is - how big is GOG compared to Steam? Based on our experience, it's a viable competitor that looks like it's on the rise. I love Steam as much as the next guy, but I love GOG's DRM-free philosophy, and their developer support is top-notch. As a developer, it's great to see there's more than one game in town.

We just posted a full sales stat breakdown for our game Defender's Quest on Gamasutra, comparing sales from all sources, including Steam and GOG:

http://www.gamasutra.com/view/feature/186940/defenders_quest_by_the_numbers_.php

Bottom line:
Gross: $286,646
Sales: 40,451

We would never have had the confidence to do this without other developers who have shared their stats in the past, so it's only fair we share our numbers now.

Chief takeaways:
1) Direct sales are still #2 source of overall revenue (but GOG's sales velocity is higher)
2) GOG is a *real* competitor to Steam
3) Browser based demo was key to our success
4) Desura/Impulse were a disappointment

Your results may vary, this is just one data point and there's still no proof that we have any idea what we're doing. Hopefully this information is of interest to someone!

yeah someone beat you guys to the puch
http://www.gog.com/forum/general/defenders_quest_devs_release_gog_vs_steam_vs_direct_sales_numbers

but it's cool to hear a bit more of your guy's take on it.

Just wanted to say that I was one of the many people that decided to make a purchase after playing the browser demo. It was definitely the deciding factor for me. DQ wasn't even on my radar until then. DQ was a great game and I look forward to future projects here on GOG.

Any way a mod can merge this with the other thread?

I imagine how much of a competitor GOG is would be directly related to the type of game. In other words old nostalgia styled games would sell better here than more modern ones with Steam features and whatnot.

The online demo is definitly a good move. I remember playing it on Kongregate a long time before it was sold here and steam. I wish more did, it is I envisage OnLive et.al would be good for. The good thing about the increase in unity development is that it is also easier to make web versions...

Anyway - the sale spikes is interesting, especially comparing the Steam and GoG spikes. Also good to see the high amount of direct sales you had.

the other thread seems more interested in using the numbers so they can calculate SS2 sales anyway...

Not sure how you came upon that conclusion seeing as how there isn't a single mention of SS2 in the other thread as of yet.

ha- no I only looked in on the first post there which says "This is particularly interesting for those hoping to convert the bestsellers list in to sales: " and nothing else. Considering the other thread... I did not bother open it up again.

Anyway, I see it did not take that turn. I was jumping to conclusions.