The
Hipshot Tremsetter allows you to have a good return to pitch, and a way better tuning stability. It's a spring loaded device that you have to put in the middle spring place of the tremolo system.
Donno about that WD trem stabilizer, but think it's a similar thing, just another brand.
To me, the best thing ever made (but, like all best things of the world, no more available), is the
Ibanez BackStop system: I got one on my '87 Radius and... damn, it works great!
It allows you to get a perfect tuning even in case of a string break.
Also, like the Hipshot, it maintains the tremolo always at perfect tuning. God Vai uses it too on most of his guitars.
Many ppl say that those devices give the tremolo a bit of stiffness. It's true, but it worth it!
my €1.00
nuno