Not for me
Here is the FAQ for Amazon MP3 downloads: http://www.amazon.com/gp/help/customer/display.html?nodeId=200154210
And here are the reasons I won't be using the service:
1. The downloads are in .MP3 format. I don't want the patent-encumbered .MP3 format. The only .MP3 files I have are from the now-defunct mp3.com. All of my own CDs, I rip to the free .OGG format.
2. The tracks are encoded at 256kbps VBR.
While some (probably many) will point out that if I "purchased" a track, I could convert it from .MP3 to .OGG format, I would kindly point out that any conversion to/from a lossy format will result in degraded audio quality. In other words, the resulting .OGG file would be even less quality than the .MP3 file, no matter what bitrate was selected.
3. No physical media is transferred.
I like CDs. I like being able to play the music in my car and in my CD player. I like the fact that if I want to, I can re-rip the songs into any format I want, including lossless FLAC format.
4. You need to download and install the "Amazon MP3 Downloader" application in order to "purchase" the album (you do not need to install the application in order to "purchase" the tracks individually, though doing so will often cost more than "purchasing" the album). This also excludes Linux users: "If you wish to purchase an entire album, you are required to use the Amazon MP3 Downloader available for Windows XP or Vista and Mac OS X 10.4 or higher."
5. You cannot download the track again if something happens to your computer. "Your Amazon MP3 Music purchases can only be downloaded once. After you have successfully downloaded the file to your computer at the time of purchase, we recommend that you create a backup copy. We are currently unable to replace any purchased files that you delete or lose due to a system or disk error. If you encounter a problem with an MP3 file immediately after purchase, please click the Customer Service button in the Contact Us box in the right-hand column of this page so we can determine how to help you."
This also means that if there were artifacts introduced during encoding (pops, clicks, etc), and you don't notice it right away (perhaps even if you do), you're screwed and you simply have to deal with it.
6. The license is non-transferable.
At least with a physical CD, I can resell it if I later decide I no longer want it.