I am not the one that voted, but I will tell you why I like combo edges.
I understand the whole "they don't give you enough of either to be useful" arguement, but I disagree with it.
I have never in my life needed more than an inch or two of blade. My Activator has done everything I have needed a knife to do. I know there are times where more blade is needed, or helpful, but I rarely encounter them.
So, since I don't I need more than a couple inches of plain edge to do most everything that *I* have to do, then if my knife has a 4 inch blade, I feel the extra length can be put to better use than more plain.
Since I really like big knives, I often find myself in that very situation. I want a big knife, but I feel all of that needless plain edge (past the first 2 or 3 inches) can be a waste (but isn't *always* a waste as I also like large plain edge knives too).
I feel I can get most things done with a little plain edge or a little serrated edge, so a combo edge is like having a plain Activator, and a serrated Activator in one knife.
Now, I understand that when you want a plain edge that having less plain edge means you may have to do more work. If the cut requires a draw, then you run out of edge sooner and have to "saw" back and forth more often. The same goes for sawing with a serrated edge. However, using a plain edge for a serrated job or a serrated edge for a plain edge job also requires more work... so...
I think a combo edge does everything okay. It makes you work a little harder at everything, but not THAT much harder. Edges that are purely one or the other are great at some things, but worse at others. I guess the controversy is whether or not using a PE for a SE job is harder than using a CE for a SE job. I feel that a CE is better at a PE job than a SE is, and better at a SE job than a PE is. My experience has taught me this, but that is based on what *I* have to cut on a daily basis.
There have been several times at work where I have to cut something and found that simply touching the material to the serrated portion of the combo edge cuts it instantly. Like a laser! So I didn't need more than a tooth or two of serrations. While the plain portion would force me to work harder. Using the same knife later, I have had to push cut with the plain portion, and was glad the knife wasn't fully serrated. When push cutting, you don't need extra plain edge.
If someone is willing to carry two knives, then this isn't an issue. But I often want to carry only one (and other times I will carry two, but it depends on what I am wearing and how much I want to carry), so having both edges on one knife can make for less work than just one or the other. Or rather, it can be like two smaller knives in one space.
But don't get me wrong... the first time I used my very first knife (a combo edge) I noticed that having the serrations there made the 3.5 inch blade feel like a 2 inch blade. The serrations got in the way. So I can see the other side. But especially for larger knives I feel the downsides are worth the benefits to versatility.
All that said, I own and will buy knives that are plain, serrated, or combo. It really depends on the specific knife. I often will decide just based on looks, or my preference at the moment. But I see the advantages of all 3 of them, and they all do have advantages.
For a very small knife, I would tend to not want a combo edge.
And just so you know where I am coming from, I work at a newspaper warehouse and need a knife to cut plastic bundle straps, plastic stretch wrap, tape, cardboard, rubber belts, and a lot of other random stuff that pops up.
All in all, though, I have found that all of my quality knives will do everything I need them too. I can bring my SE Pacific Salt and it will do pretty much everything. It might be harder to do certain jobs, but it will do them. I can bring my PE Military, and it will do pretty much everything. The only times a knife of mine could not do the job at hand at all is when they are too big to fit into the inserter machine to cut out a jam. Many of my big knives are too large to get into the nooks of the machine.