Jon and I were just discussing this and I'm keen not to put people off who might be feeling reticent to share stuff.
It's totally fine to post commercial projects. This isn't a freeware-only forum.
It can also be helpful to post progress updates without even specifically request feedback, as long as the spirit is about sharing progress and process rather than "get hyped!". People will (hopefully) chip in with thoughts. Thinking out loud is great, especially if you don't live in a city with game-dev meetups, etc.
Playable, work-in-progress things (+100 points!) are ideal. Screenshots and videos are ok (+10 points!), but I find it really hard to have any constructive thoughts based on them, unless it's a hyper-specific issue. Ideas and design notes are also fine (+5-20 points!?) but only to a point.
If your first post in a topic has links to greenlight (-50!), ludum dare (-45!), kickstarter (-100!), PR-focused blog (-37!), a company logo (-5!), then I'll assume you're here to harvest eyeballs and build brand awareness rather than share and discuss development.
I feel like there's also a discussion to be had about how to GIVE good feedback too, but it's more subtle. I think the onus is largely on the requester to set the right tone, give enough material and filter/process stuff they receive.
Some less obvious ways to use this forum for feedback:
- If you're not comfortable posting a build publicly, ask if people would be up for receiving a build via email and sending feedback that way.
- If you need to test how a game plays and works in real time, see if anyone is interested in playtesting via skype (voice + screenshare) or just via IM. It's not quite as good as sitting next to someone watching, but can be great for finding those spots where the game just isn't communicating like it needs to.
Both of these are higher-investment (on both sides - so bear that in mind) but can be extremely useful at certain points in development.
(I was going to write some concise bulletpoints here but it turned into a fucking wall of text. Sorry, maybe elsewhere)