Aurgh! I posted and promptly forgot about it; my apologies. To summarize the responses:
Those of you who have regular packing cubes overwhelmingly said they like them because it helps with organization.
The few who have tried compression cubes did not say they were ditching their regular cubes in favor of compression ones, but I appreciated Janet's point that she sometimes uses her compression cube uncompressed. Lisa (LJP) and Laurie mentioned that they would be good for winter sweaters and storing out of season stuff. JAileen had the same frustrating experience as an online reviewer, that it didn't work for the intended item. Like RobinF, I would worry a bit about going over weight limits, but I own (but have never used) one of those luggage scales.
Peri, Irina, and Ummlila: I don't worry too much about wrinkles; a small mister works for me most of the time. The one reviewer I watched said compression cube wrinkles weren't a problem, but we all may wear different types of clothing and fabrication.
I don't use my large packing cubes as it is, but I can imagine using that size in compression cubes for storing bulky sweaters per LJP. I roll my current clothing pretty tightly into my packing cubes so I don't know how much more room I would get with compression. Truthfully, it's the footwear that takes up all the room!