I can definitely hear the difference through my Grado headphones - more so on my own tracks than on the video of course. I don't consider my ears to be very well trained at all, and sometimes have a lot of trouble hearing subtle effects like compression. Yet I can hear the CE. It adds a little more presence, especially in the high end.
With regard to placement in the PC, I mentioned in another post that the CE seems to add quite a lot of extra frequencies in the low to mid region as well. You can see this if you put a strong high pass filter on a track so that only the highest frequencies are coming through, then put the console emulation AFTER the EQ. With the CE turned off, there are no low frequencies at all. Turned on, you can see exactly where the CE is adding frequencies and how much, by looking at a frequency analyzer. The different types of CE behave differently - the S-Type seems only to add very low frequencies, whereas the other two add frequencies all the way into the mids.
What this means is, if you're using a high pass filter to control mud in your track, then the console emulation is going to add some of the frequencies that the filter has removed. So if you use HPF's to this end and you don't want any new lows added, you might consider putting an EQ with a HPF
after the console emulation on the track.