Hi Bit,
I never tried the free one. I do have Waves doubler and to be honest, it confused me when I went to use it on a project and I never dug deeper into it. I may have overlooked a perfectly good solution, but I tried the demo of Microshift and was hooked. I heard it referenced in a mixing video on You Tube and I REALLY wish I still had that link. The engineer was talking about using that and bx_Saturator for metal guitars and I bought that too (and it is really awesome).
I seem to have an affinity for these Waves Abby Roads plugins and when I read the ADT stuff and saw the pretty GUI I just had to try it. A few minutes playing with a vocal and I was sold. I haven't even tried the manual settings - just used the presets and was blown away (and things MOVE in it, you know it sounds better when there are animations of physical objects, like tape reels and such :)).
So, perhaps not the soundest decision to skip the Doubler even though I have it or not look at the free one (too damn ugly, I am shallow), but I really do like the Microshift and the ADT a lot. They make me all warm and gooey inside. :)