i use the candi sugar quite often. pretty much everyone on here agrees with your statement here, but i just use it because i trust it and i am willing to pay the price. i am scared to use table sugar because i am worried that the beer will not taste the same.
You should really try it yourself. If you can talk Joe Fleischman out of a bottle of his Westmalle Tripel clone, I believe he uses sugar and his beer was outstanding. A personal plug for Joe (great guy to talk to and makes a great beer), and for using table sugar. But you will never know for sure unless you try it yourself.
on the other hand, i have not used the soft candi sugar that northern brewer now stocks. how does that compare to the rock sugar?
Some people love it, some people do not notice a difference between the blonde soft candi sugar and table sugar. My guess, from listening to and reading from other brewers, is the blond soft sugar can add some subtle flavors that some do not really notice, the soft Belgian brown sugar has a subtler effect than the dark candi syrup that I believe somebody (I believe it was N8, but do not quote me on that) said he did not really notice much of a contribution. I have tasted a homebrewed beer that had some of the blond soft sugar AND some dark candi syrup that was excellent, but that could have been because it was just a sensationally brewed beer.
What my research has kind of lead me to conclude is:
1) If I want a Tripel, I will use Pilsner Malt and table sugar. It tastes great to me that way as long as I don't screw anything else up along the way.
2) If I want a Dubbel or Quad, I will use one or two bottles of Belgian Dark Candi Syrup. It seems to make a more noticeable contribution, taste amazing, and can be used by itself or with Special B to make a great authentic-tasting Belgian Dubbel/Quad/Belgian Dark Strong Ale/whatever-you-call-it.
3) If I were using anything else, I would use some of the many ethnic sugars out there. They cost less, seem to have more of an impact, and are more tried-and-proven than the rock sugar from almost all accounts.
Taste is subjective, and I am not REALLY a Master Brewer, but I have had personal success, and tasted others make amazing beer, using table sugar and the Dark Candi Syrup. Those have been successful in really nailing the flavor(s) I was looking for and love, so I feel no need to look anywhere else, although personal experimentation is always worthwhile so try everything.