More than 1.5 years after asking this question, I'm right now on SQ 34, flying to SFO in Premium Economy. Boy, SQ's quality has dropped quite a bit since I first flew them a couple of decades ago. The seats are ok. No better than the PE seats on UA or LH, but more comfortable that UA's E+, as one would expect. I've had one meal so far, and it's been a disappointment. A potato/cauliflower salad where the main flavor was mayo. A chicken dish with a small amount of chicken (which tasted ok), lots of unremarkable fried rice and a few boiled leaves. A tasteless roll and crackers to complete it. I had a far better meal a few days ago in economy on a 3.5 hour flight on Air Astana. And this one is a 14 hour flight.

A few months ago, my wife flew SQ SIN to SFO in business and she was thoroughly unimpressed. She said the hard and soft products on UA's Polaris, LH and even AI's newer planes are far better than SQ. Now I can see why she said that.

Bottom line: not flying SQ again unless their PE prices are not much higher than UA's economy prices. But most of the time, SQ's economy tickets are more expensive than UA's Y, so the chances of great PE prices are very, very low. Add to that the 500 PQP limit on these long flights, it makes 0 sense to fly SQ again. I'd rather take more circuitous routes and break my journey if I don't want to fly 14+ hours in Y on UA.