Topics:
1- skimmers - H
While I came into the hobby post-skimmers, it's hard to imagine the impact, however starting with a simple air stone powered skimmer, I can definitely see where they ended up with micromeshes, needle wheels, super tiny bubbles, massive volumes.. all sorts of great stuff, so I have to say they're a big thing out there. They may not have been hot stuff when they started, but in all honest most influential things are not.
2- halide lighting - H
Really high intensity lighting, relatively low wattage compared to incandescent bulbs, nuff said.
2b- fluorescent lighting - M
While the colors to make things pop (actinic) are great, and there definitely was a power savings, they're a moderate impact at best, they really stepped up with the HOT5 bulbs, but ... yeah I've never been particular impressed with them.
3- shipping methodologies/quality on arrival - H
I don't know what it was before, but I'm guessing the poorest shipped of corals today probably are well beyond what used to be done.
4- coral farming - M
While not big for me, since everyone in our club is basically a farmer, and lots of near by stores are farmers, I think places like ORA really hit home in other parts of the country, and I don't want to bias myself because we're a tad spoiled out there
5- fragmentation - H
HUGE! Absolutely HUGE! Not sure this is an advance though, corals have done this for centuries!
But the idea you don't need a whole coral, really has hit home. If the hobby today was full of colony sized pieces only, our reefs would be in really bad shape. Plus the ability to "bank" your corals by fragging and giving away, if you lose your coral you can always get a piece of it back is huge!
6- live rock availability - L
Eh.. can't really say much about this
7- nutrition/food - M
I'm sure good food for fish has jumped light years beyond the idea of feeding brine shrimp, and coral/tank foods are great, but yeah.
8- quality media/disbursement of quality information - H
Awesome, seriously before I found this site, RC, and a couple others the only place I had for information was from LFS owners (dubious) and books (that were usually at least a decade behind the times of where the hobby was).
8b- internet as information source - H
Add to 8
9- increased activity - local, regional, national clubs - H
Hard to say exactly how clubs have worked elsewhere, but if I take my local regions as an example, fantastic, I'm sure I would have yanked many corals (indirectly) out of the oceans, and probably wouldn't even have half the tank I have now.
10- Berlin method - L
I'm sure it was good, but IMO it's another way to do it is all, I wouldn't consider this revolutionary.
11- other? - Umm hell wide-high flow/low wattage pumps! - XH!
Seriously, flow is way more important than lighting in most cases, and getting turn over rates of 30x, 50x, 80x in a tank, has been troublesome in the past, where it seems like most in tank pumps max out in the 300 gph range... now we have 1500gph, 3000gph, 5000gph pumps! So even the largest of tanks don't have to rely on ultra-expensive and power hungry external pumps pushing stuff through a closed loop.