Mind you, I have not set up a tank again (yet), but I started paying attention again about a year and a half ago. Big changes that I've noticed:
Live rock - most tanks start with bleached base rock. Gives you a clean slate without pathogens or pests from the start. Seems like tanks take longer to start up without the initial influx of bacteria, but in general this seems like a positive change for both tanks and the reefs.
LEDs - The previous posts seem to have covered this, but LED lighting has come a long way. There are still hold outs to MH and T5 lighting and frankly they're still viable options. LEDs seem to be offering similar results with lower power usage and more flexibility. Personally, I feel the flexibility is a double-edged sword though and some can't fight the lure of constantly tweaking settings. Don't.
Refugiums - I feel like this has even advanced more in the past year and a half, but the value of a well lit refugium has been pretty well demonstrated. And not running off of a dinky 15 watt shop lamp. Search youtube for the Bulk Reef Supply videos on refugiums and you can see what a value having a fuge lit with proper spectrum and intensity.
DC pumps - Another double edged sword. DC pumps have added a lot off efficiency and flexibility to moving water around. Personally, I feel like they have their uses, particularly for wave-making and powerheads, but I still prefer the tried and true Iwaki / Eheim / whatever AC pumps as primary returns because of their tendency to last for decades.
Aquarium controllers - These were in their infancy a decade ago but they're becoming more and more popular. Being able to monitor & maintain the tank remotely and autonomously has huge value. That said, I'm not a fan of funneling every device through a single potential point of failure. Again, they have their uses and they really seem to be a leap forward in the hobby, but there are potential pitfalls.
Tank raised corals - My perception is that only a small minority of corals are still coming from the ocean. There's also a premium market for 'named' corals that is frankly off the wall.
Tank bred fish - these are becoming more and more common. You'll pay more for a fish that was raised in a fish tank, eating commercially available foods and dealing with the rigors of aquarium life. Things like clownfish are also being bred for particular colors and features. To the point that some barely look like clownfish. I'm personally not a fan but love the general idea of tank bred fish.
Local Fish Stores - The availability of the local fish store is waning. Frankly, I feel this is the worst trend in the industry. If you have a good local fish store, shop there. Many are barely hanging on. To the detriment of the hobby, IMO...
I'm sure there is more but that's my perception of the big changes... Good luck!
