I was just looking into this because I got the "Accessories on sale" email. So first of all, a thread bump since it's now only $20 instead of $30.

After looking around briefly, even the generic ones on Amazon.com appear to be OS specific. The Trendnets seem to be made for PC (not Mac OS X) but someone in the comments reports being able to download additional drivers to make it work on the newest Macbook Air.

It's too bad because we now have no computers with ethernet ports when we're on the road, having both switched to Macbook Airs. The edge doesn't have one and my N810 doesn't have one. I was hoping to find a generic piece of hardware that could be used with either the edge or the macs, just in case we ever need it on the road. There have been a couple of times where it would have been handy, but at least we have a travel router so if we absolutely need to connect via ethernet, we plug that in, then connect a machine through its wireless signal. But if they're so device-specific, I just might pass on one.

But if you want one, at least it's a healthy sale price now!