Old school for me too. While I've never run biopellets, I did follow the vodka dosing bandwagon. Let's call this what it is: a way for companies to capitalize on people that carbon dose (or want to) by offering a replenish-able product in a pretty package with a nice expensive reactor. While they're great at lowering nitrates (like vodka, vinegar, etc.), phosphate is a whole other story. So, you feed more because you can and your corals need it, all the while exhausting GFO at a faster rate because your tank is NO3 limited and feeding a lot more food. My SPS got pale, many receded, and the tank never flourished. I always felt like I was waiting for the next battle. I got cyanobacteria like clockwork every 6 months or so, and hair algae from all that food I'd been feeding caught up with me when PO4 started leaching from my live rock.
IMHO, it makes much more sense for me to stock my tank within reasonable limits with fish, feed them a good varied diet, run GFO and do a 10% bi-weekly water change. I think back to when I reached 0 nitrates and had to start dosing amino acids and feed more and laugh. Now I realize I could just keep the tank a little more "dirty" and get better results. In my new build I purposely keep nitrates around 5 and phosphates between .03 - .06 on a Hannah meter. I have better SPS colors and growth than I ever had while carbon dosing. I believe there is definitely a benefit to having some measurable nitrate in the water column for good coloration and overall health of a reef system. I think that in the back of our minds we feel we are less of a reefkeeper if we can't reach undetectable levels of nitrate and phosphate. I'm now of the opinion that in low, measurable levels they're exactly what a closed system needs. Running a ULNS keeps corals on the edge, where one slip in parameters, lighting intensity or change in feeding regimen is almost immediately seen in SPS; for better or worse.
I prefer to see slow changes in my corals and monitor accordingly based on what I've learned so far in keeping SPS. For some people that have a well trained eye and more time to fiddle with their systems, biopellets, vodka, vinegar and Zeovit may work. I think the problems we're seeing arise when people new(er) to SPS follow a trend and look for a silver bullet. There isn't one. In anything we do (reefkeeping or not), when things go astray it's time to revisit fundamentals and the basics. Keeping SPS corals happy, colorful and growing long term really has no secrets or magical potions. Stability, patience, time, good husbandry/maintenance are inherent in any SPS system; whether it's ULNS or not. If you're new to SPS, a ULNS should be seen as an advanced level technique to tweak and build upon what you've already learned, but not as a failsafe to help you sidestep nutrient control.
For now, I'll pass on biopellets and all the other ULNS "stuff".