@B.G. -- My guess is that she doesn't weigh the same as you -- am I right? If so, the problem is that her skis weren't the appropriate size for her weight. If not, then yes, it is about technique. If you get Nordic skis with lots of camber and you are a bit light for them, then you need to really jump on the skis to get them to move. I have a pair that I struggle with unless I am on really flat ground (or I'm wearing a heavy pack).
I think Ryan has a point, but there are a lot of other factors. As Roger suggests, a lot has to do with camber. Ryan emphasized this (he said "fish scale skis without camber") but it might have been lost in the comment. I have a pair like this (Atomic Lite Terrain) and they are extremely slow. But they are also short and sculpted. There are so many factors involved that it is hard to make generalizations, although I think Paul's comments are spot on. I agree with Ryan that a ski without much camber (or none at all) will be slower than a flat bottom ski. It is also harder to wax that area (most people, including me, don't). This means that you have a ski that is great when first bought, but gets slower over time. Cold waxes and products like maxiglide can help a lot, but they are nowhere near as fast as a hot wax (I'm not sure what is applied at the factory, but it is really fast as well). Plus, when you add the stuff, you can mess up your uphill grip sometimes.
That being said, I really like fish scaled skis -- I think with most skis, the difference in speed between fish scales and flat bottoms is minimal. Meanwhile, if the terrain isn't too steep for them, then fish scales are much faster than skins or kickers (in my experience). I have done Smithbrook several times, and I cruised along just fine with fishscale skis (both up and down). Like I said, there are so many other factors involved (like the last time you waxed your skis) that could easily contribute to the feeling that your fishscale skis are significantly slower.
@Dan -- I would get the wider ski. Generally speaking, wider is better. They are called "powder skis" but really, the biggest difference is on wet, sloppy snow. Snowboarding became really popular at Mount Baker, which is not known for powder, but for huge, wet, sloppy snow dumps. A big ski (or snowboard) allows you stay above the mess, and carve nice turns. I've tried skiing sloppy snow with the aforementioned Atomic Lite Terrain and it was a disaster. I sunk too much so I was trying to push heavy snow with boots that weren't up to the task. On the other hand, with powder, you can ski it with anything -- it's just that you can ski it more enjoyably with wider skis.
Back to the original article, for the most part, you can put any binding on any ski. For example, I have a pair of Atomic Rainier skis with NNN BC bindings on them. There is no reason why I can't replace those bindings with a Telemark or Randonee binding. So the idea that a BC Nordic system is lighter because the ski is lighter (which was suggested more in the referenced article and not this one) is silly.
With that in mind, high quality Randonee boots and bindings are simply lighter than Nordic BC boots and bindings. However, there are plenty of (relatively) cheap Randonee (and Telemark) boots that are heavier than BC boots.
Comfort is a different story. It is hard to generalize on the subject of comfort (put your trail runners on the wrong feet and suddenly those heavy hiking boots seem a lot more comfortable) but ankle motion is only one type of motion. As David mentioned, the lack of metatarsal bend means there will be less efficiency to each stride and, in my book, a lot less comfort. Likewise, the main advantage of plastic boots becomes a disadvantage when you are talking comfort. Soft boots flex in various areas, which is really nice when hiking or skiing. The price you pay, of course, is that they have less control. If you manage to find enough control with a soft, flexibly boot, then you are in heaven (e. g. I've skied the aforementioned Smithbrook on regular (non-BC) Nordic gear and it was a blast). But if you misjudge the conditions, you start wishing for a plastic boot. A good compromise may be Telemark gear. They have the metatarsal bend, but all of the control (or at least almost all) that a Randonee system has. You pay a big price in weight, unfortunately. Just as no one is making big advances in Nordic BC gear, the same can be said for Telemark boots. Even if the boots matched the weight of the fancy Randonee boots, you would still pay a sizable weight penalty for the bindings (and it might be impossible to rectify this, give the design limitations).
Unfortunately, Randonee race gear is designed to win races, not be more comfortable. The range of ankle motion and relative comfort advantage is a side benefit. Most of the people who find the boots surprisingly comfortable come from an alpine skiing background. There are very few cross country skiers who will say "Wow, these plastic boots are really comfortable". They will, on the other hand, comment on how surprisingly light and expensive they are. I think the ideal boot would act like a Nordic boot on the way up, but an AT (or even Telemark) boot on the way down. I could see having a basic inner boot much like a regular Nordic boot, but with a plastic shell that could be applied for the way down. Since there is a transition with AT gear anyway, this would be a small price to pay. Such a system would weigh more (and not win any races) but would be fairly light going up and would basically be my dream system.
Speaking of transitions, that is one of the other key advantages to BC Nordic. Ryan eluded to this, when he said that the fish scales slowed his skis too much going down, and he was forced to skate, or stop and switch to uphill mode. With BC Nordic, this isn't an issue. I've gone on rolling hills where switching between uphill and downhill occurred every couple minutes and BC Nordic with waxless was extremely fast. Of course you can ski those sections without going into downhill mode, but I think with BC Nordic you have more control (since those are designed for that).