The Whammy DT is an amazing pedal.
Personal Uses:
It provides me as a guitarist the ability to harmonise with myself, this is perfect if you wish to play anything like Iron Maiden, Judas Priest, Avenged Sevenfold, Kiss, Pantera if you can figure out what interval (harmony is being used) you can play literally any dual guitar riff/solo.
Features: The Whammy DT comes with a momentary foot switch on the 'DT' side which is extremely useful if you are playing a song in E and wish to drop tune to D (whole step down). The oct up + Dry is a really lovely feature if you are playing a clean song and want to emulate the sound of a 12 string guitar.
The Whammy itself track really well, it is a fantastic upgrade from the Whammy IV.
Sound: The sound is fantastic, there can bit a little noise (high pitch buzz) but if you have something like an Boss NS-2 it will clean up the signal just fine.
It works really well with a distorted signal, arguably it is as good with dirty signals as it is with clean ones.
Quality: It is cased in a solid metal chassis so there is no worry about it breaking, the only downside is that is can be tricky to change between the different settings e.g.
'1 oct up' - '5TH down' there is one simple solution for this though, purchase the Digitech FS3X Footswitch Pedal, this enables you to select which mode you want to use and go up or down on the display via 3 footswitches.
Overall : I believe the Whammy DT is a fantastic pedal, it can be used for any type of music, it also works well with bass but the Digitech Whammy Bass is specifically designed for bass, anyway, the pedal is a brilliant piece of kit and a fine addition to my pedalborad, I would strongly recommend purchasing it if you have the desire/need to.