In my previous post I was referring too the material that was a bit wild and has some form of out of control dynamics. But what about material that is consistent and well balanced level wise over time. Pre mix editing can also tame dynamic material well. So it is not hard to get things right before you apply any effects. On even material then parallel compression could work and sound quite good. But then you may not hear the effects of the parallel compression so much either.
 
With parallel compression a sudden loud sound can sneak around it easily but when things are in series it becomes a much harder trap for that wild change and it comes out at the right level at the end of the chain. Provided you have things set nicely.
 
Studio One has put Wet/Dry mix controls on all their plugs now and that is handy. Sometimes even with a normal compressor in series it can make the sound seem like it is slightly back in the mix and bringing the dry signal back in can be just the ticket for getting that sound to sit back in the mix where it was before. The other way to do it is to be savvy with the makeup gain control. You have to be prepared to use it and put back any missing gain. K metering is handy here for checking levels rather precisely before and after compressors.
 
I find the dual in line approach nice on vocals. I can get it to work every time.

+1 Danny on the PC buss compressor. I use the wet/ dry knob a lot on the drum mix. I usually get everything happening just the way I want it to sound, set fully wet. I take a break and come back later, to let my ears rest, then roll between wet and dry until everything sounds full, but open in my mix.

I have done this a little bit on vocals with success as well, it all depends on the song.

I use it for instruments that need to be audible all the way through the song but also have some loud dynamic passages that need to rise above the average level. Snare drum is a prime example. Maybe bass guitar too.
 
I agree with Danny & others though. Don't use it unless you need it.