I just bought a Headstreamer and arrived here because I had some of the symptoms this thread highlights.
I haven't worked on getting it functional with my Linux machine yet. My Music Streamer II works great on that machine; I love it. The Headstreamer volume control doesn't work yet, and based on previous experience with sound on Linux, I assume the correction will be the result of changing something on my system, and is not going to take tons of work, though I expect to get annoyed at ALSA or PulseAudio as I have many times before.
I got concerned when the Headstreamer wouldn't quit with the popping and stuttering on my Windows 7 machine. I anticipated issues with WASAPI and I tried every solution proposed in this thread, with no success. I tried several players.
Then I connected the Headstreamer directly to my computer so that the Headstreamer is not sharing a USB root hub with any other device. It now works flawlessly. So perhaps this issue ought to become part of the Headstreamer literature (or lore): sharing a USB root hub can cause symptoms that sound a lot like WASAPI, buffer length, etc. issues.
In W7 (I don't know similar stuff in Linux -- at least Fedora -- because I've never had this issue with Linux), you can see what devices are connected to which USB root hubs, and assigned to which controllers, in the Device Manager. W7 says that the Headstreamer is a 250 mA device, so power could well become an issue depending on what devices share a root hub with the HS.
I can make my HS misbehave by connecting it so that it either 1) shares a root hub with another connected device, or 2) is part of a port network that necessarily shares a root hub with several others (as in typical front-panel ports, of which my computer has several that share one root hub and are amperage-limited to a level below 500 mA). This is easily remedied on a desktop-like system with lots of root hubs and ports; I can see it might be more of a problem with a netbook that is hub/controller-limited. But maybe this issue is rare. If I plug the HS into a cheap generic USB hub (the external port-adding kind), I can really make the HS sick. It pops constantly when connected to this hub.
Some users on this thread report that other devices work fine when connected to the same port that the HS was connected to when causing problems. Maybe those devices don't have this sensitivity, or use less power?
In any case, this was a very cheap and easy fix for me. I have found the sound quality coming out of the HS through my HD-595s to be worth this negligible trouble.