I just completed my first purchase at the new Amazon MP3 Store. The purchase was painless. They have a plugin you can download to manage downloads, but its not required - I downloaded the song with nothing more than Firefox.
Amazon offers 256kbps, DRM-free MP3 files - pricing varies a bit, but most songs are $0.89. 10 cents cheaper, no DRM anywhere...Amazon is going to give iTunes some real competition.