I'm another one of those that has been reading through these kind of discussions for years. Up to now, all I've done is pretty much ask gear questions, except for back about 6 years ago, when I was getting going and trying to move from a 'groomed blues' skier to more advanced, I asked a lot of questions on this forum such as 'how do I turn' ;-) .
First, a little 'history'. I grew up in Puerto Rico.. so no skiing there. Moved up this way (upstate NY) for college, learned how to ski, moved to PA.. didn't ski much. About 8 years later (1999) I got into it again (fun ski trip to Austria). I was no more than a so-so intermediate, but I started getting obsessed to becoming the best skier I could be. I wanted to ski all that hard stuff I couldn't ski then. One key 'gap' for me was bump skiing. I was skiing Killington a lot.. and there's bumps on most of the advanced trails (and in the trees), so I had to learn bumps.
I took a local lesson with a local instructor. It was good. Taught me how to 'ski the slow line', as you guys call it. Taught me how to navigate bumps and how to have fun going down the bump trail. However, for me.. something was missing. I would see those guys skiing the zipper line (the 'fast line'), and I would be in awe. It looked hard, it looked like fun. So one weekend in 2000 (or 01, can't quite remember), I took a class with Mogul Logic (Chuck Martin) when they came to Killington one spring. I bought bump skis, tried it out. I totally sucked.. but I was also hooked. Since then I've gone to the summer camp at Whistler a couple of times, and have gone to one of the yearly 2 day winter sessions for a little yearly 'tune-up' (I guess I've done 5 of those now?).
So, all that said.. this is my take.
Yes, there are clearly a couple of general schools of thought on how to ski the bumps; what you folks call 'the slow line', and then zipper line skiing. I think they are both valid, depending on your goal. That said, and having some experience skiing both types, I'd say the following about the zipper line
If you want to go FAST, the fastest way down is the zipper line. Not skiing the 'fast line slow', but skiing the 'fast line fast'. Personally, I am still skiing the 'fast line slow'. I am finally seeing some breakthroughs and can ski the zipper line with ok technique. However, I am still very slow. But.. I think this year I finally saw the breakthroughs which I need which will allow me to start stepping on the gas without killing myself.
It takes hard work, especially if you've been skiing a while using other techniques (it has got to be much much easier for people starting this as kids). It is not a simple process. There are a ton of different mechanics that need to happen even on flat land turns using mogul technique, there is the whole absorption thing, lots of muscle memory that needs to be ingrained, and it is fundamentally a different turn than what most people are used to doing (all at the knees - but you also have upper body position being key, vision, hands, etc). It's taken me 5 years and I am finally feeling like my technique is falling into place.
When done right.. it doesn't beat you up like people think it does. It doesn't kill your knees, it doesn't kill your back. When done right, you literally feel like you are floating down the bumps without any impact. The thing is.. as I said above, it is in fact a long road to get to that point, and if you don't have the proper technique yet.. you are liable to get beat up some on the way to learning it. But we do have guys of all ages on the classes, so it's not an age thing. I am 38, and most of the folks on the adult classes are in their 30's to their 50's. Now.. don't take me wrong.. I am not 100% there yet. I still get thrown around often. But I always have a couple of real good runs where I do everything right.. and it is awesome. So, I know how it feels when done right (I just have to get more consistent with it).
One last thing. When you finally start getting it.. boy, it is so much fun.
Oh yeah.. I forgot. Very addictive. Most bump skiers I know are very obsessed with bump skiing. We ski in bump skis, we dress in freestyle stuff that perhaps we are too old to wear, we watch Freestyle World Cup events as if it was porn (or this cool website - www.skidebosses.com
, check it out). We talk about it all the time. And yeah.. we spend lots of money going to camps and such. But it is a GREAT community to be a part of, with people from all sorts of backgrounds. Great, fun people. Just a little nuts, but in a good way.
Anyway - so.. that's my take. If you have the time/energy to learn it (and it may take a few years), I highly recommend you try to learn it (but I am clearly biased, and be prepared to get sucked into a whole new skiing sub-culture). If you don't want to take the time, or subject yourself to a few years of frustration and sore-ness, but still enjoy moguls, perhaps the 'slow line fast' is the best way for you to approach it.