By PC, I meant ProChannel. I figured you downloaded the Windows version of the bundle.

Ha. One more piece of the local lingo I need to pick up on. :)

That one trips me up all the time :)
Especially since Mac is brought up here like every other thread (really weird for a forum about a PC-only DAW).

There are ample compressors out there and even a bunch ready for the ProChannel. Each may have their own merits on top of being one more compressor.

The CA2A works really well. Whenever you try it out you might just choose that one for the track because it smooths really seamlessly. Or, you might add it after you've already piled up other effects prior in the signal chain.

It's simply a really excellent module in the ProChannel collection.

I'd say this about any LA2A emulation, or the real thing itself: It's a design that's great for stuff that's not very attacky. So great on vocals, great on non-twangy bass, can be good on organs and pads. Less useful on guitars, drums, pianos, etc, unless you're after a noticeably non-transparent compression.
 
For the CA-2A, I'd have to check, but I think it's the only compressor I've used on vocals for about two years now. I rate it very highly.

I use the CA2A on guitars, bass, etc.  Great at just smoothing things out.  When I use it on bass, I use it as a limiter. One of the best PC compressors in my opinion.

I was going to try and add some useful information but what's here is all you need. Agreed totally with AT's analysis, as well as the others. 
 
Note that some compressors seem to "flatter" some material more than others. The CA-2A is the best compressor I have (and I have a lot of them!!) for my voice. That doesn't mean it's best for everyone's voice, but it sure is sweet.
 
Don't forget about the Sonitus Multiband compressor. Doesn't get near enough credit for what it can do.

It is a very popular rack extension for Reason users. Only if I could get a bundle deal where you can use it in Sonar and Reason.

Craig mentioned Sonitus. I have a lot of experience with that one after years of Sonar, but never could make myself happy with it.
 
It's pretty clear now that you can't say this or that is best, just depends on how you use it and what you are asking it to do. What is also clear is that a great compressor is vital at the front end, not just at the mastering stage.
 
Thank you everyone, even if I can't address each one of your points directly. It has all been very helpful.

I really like the CA2A.  It does what it is supposed to do. It levels a track nicely.