Adding my voice to the native Linux client chorus. I use a mac desktop on a semi-regular basis and the client there is great. However Linux is my main operating system on both my desktop and laptop. I also install it, weather another OS is being installed or not, on any other computer, PC and Mac, that I get my hands on. The Chrome extension works good, and it's better than using Airdroid inside a browser window, however a native linux client that minimizes to the tray is what I'm really after.
I can honestly say that the absence of Linux client is what's holding me back from paying for the premium version of Airdroid. I wouldn't pay for the file transfer cap removal, as I have that covered with other free apps, but the other premium features seem useful enough that I'd gladly pay $20 for a yearly subscription if I could utilize them natively in Linux. I use OSX on my PC (hackintosh) as a novelty, and I avoid Windows like the plague.
I might consider a premium subscription if you released a Firefox version of the extension you've made available in Chrome. As a Firefox user I tend not to think to launch Chrome until I need Airdroid for something, at which point I have to go out of my way to get to it. Something which loaded at startup and stayed in my system tray automatically would be the most desirable option. Barring that at least a Firefox app that I could launch right after my browser loads would be the next best thing.
I know you keep saying that Linux isn't in the works but I honestly hope you reconsider, preferably sooner rather than later. We don't have the market cornered, but the Linux user base is growing at a considerable rate. Linux is also the preferred OS of just the type of power user that your app has a great appeal to. If you refuse to touch linux I hope you at least consider making plug ins for other browsers aside from Chrome (especially Firefox, which does have a large, established user base within the Linux community).
Until then we'll just have to pester you by bumping this tread until you cave in or somebody releases a comparable app with full Linux support. Hopefully it's the former.