Audio Analysis Tools
I just read suggestions for new features in future Ardour and many of them will help a lot.
For me would be most demanding some nice well working Audio Analysis Tool, which should content Peak and RMS metering(with optional responsing time),Spectral analysis and Phase checker(osciloscop) at least.
Maybe I am wrong but I think there is not such tool in Linux Audio world.
Inspiration for such tool can be great DigiCheck utility from RME audio... (Windows)