Explicit feedback is much more common than anything else, and I haven't yet seen a standard compliant device with implicit feedback in the wild. And more common means more test coverage :)
OK. This whole implicit feedback thing seems like a good idea but it smells bad.
It's been a while since I looked into this, but when I implemented the code in the first place, I had no standard compliant device to test with, so I had to force the driver into implicit mode with a quirk.
Somehow I don't feel like debugging my USB code and ALSA at the same time, while checking both sides against a standard that doesn't exist. Given the complete absence of clear explanation of how it should work in the USB specs, even if the thing ends up working, there will be no guarantee it would be "compliant" to anything...
But as I said - if explicit feedback mode already works for you, I'd stick with it.
I'm going to stick to this advice !... Thanks.