On Freefilter:
More or less what blinddogblues said. It's sort of a combo EQ and (auto, no settings to screw with) multiband compressor that learns source material & applies those settings to selected program material.
Here's how I use it:
I get my mix as close as I can to my reference. Load a
sample of the reference material into Freefilter to be analyzed. Save the analysis as a preset. Apply the preset to my material.
It's not quite as easy as it sounds though, as you have a choice of morph value and gain. It takes a bit of practice to get it right, but I've had excellent results with it. I generally tweak the mix just a bit after the processing, but it's one of the most useful plugs I have.
Samplitude has a similar filtering process, but I'm still working on it.
On the Waves Mastering plugs:
These plugs assume that you know a bit about mastering. They aren't as straight forward or "automated" as T-Racks or Ozone. I like the L2, but the others have a bit of a learning curve; not unlike the mastering process itself.
T-Racks:
Has some cool features, and it's good at getting your mix to sound "warm," but I think it's time has passed. It doesn't hold a candle to Ozone as far as features go. I've used it for a final compressor a few times, but by the time I get my mix through my other processing there isn't alot T-Racks can do for me.
YMMV, of course.