Tracktion T7 the latest upgrade, like T6 is also free - hard to argue with that as a proposition. Tracktion have long been an advocate of the single window approach to a DAW, its a simpler to use interface and makes it an ideal starting point for new DAW users. Added to that is the multi-platform support, Windows, OS X and Linux.
New in T7
Tracktion T7 is available for free download now, with discounted upgrade paths to the full WAVEFORM daw.