Obviously the amount of feedback depends entirely on what you are developing and who wants it. I have a Vic20 I built out of 2 broken ones, one I bought for a quid and the other I found in a skip. Once I'd re-built it and hacked the 16kb expansion pack so I could play cartrige games using it I got it running pac-man and was really proud! The kid from next door came round cause I'd asked to borrow his sega gamepad to test out the joystick ports (I was at my parents house away from my retro collection at the time). He took one look at Vic20 pacman and said "how shit is that, I have a playstation 2". I still love my vic20 which I spent ages getting to work, everyone else just isn't interested, and thats fine. Frankly I'm not interested in an xbox360/Wii - each to their own.
You have to find people who are interested in what you are interested in, you actually have to go and look for them, cause they might not know that what you created exists. I'm happy to try anything out for a developer, I won't promise to play it for 1000 hours to iron out all the bugs, but I'll load it up, try it and give it an honest opinion, just PM me and tell me where I can download it in future.
The only alternative is to deliberately design something you know will be very popular, though it wasn't intentional thats what 'chp' did when he created win2x. I gave a constant stream of feedback on that because it was something I REALLY wanted to see working the best it could - many others joined in and added their ideas and suggestions too. Also EugeneP emailed me a number of builds of FX navigator to test, again it was something I found useful and was happy to help.
In short, if you want my feedback, and you arent creating something I'm going out of my way to look for I'll still be happy to give my opinion, provided YOU seek me out (shit, I like the A-Team). I'll do what I can to help out any developer who's creating stuff for the benefit of the GP2X Wiz community.