I haven't booked SQ PE due to the issues Beolab identifies:

-Seat design features a footrest, which turns out to be useless for most
-No dedicated restrooms for the cabin section which other airlines do have
-No cabin separation from Economy Class. The curtains stay open
-No pre-takeoff drinks
-Meal quality only marginally better then Economy Class
-Book the Cook orders are served first, but no accompanying drinks service. This comes much later when the Book the Cook meal is already finished.
-No dedicated cabin crew for this cabin section, resulting in only one drink
service with the meal. Refill round too late or none at all.
-Champagne in all advertising, but only available on request
-Drinks served in plastic cups, not glassware
-Overpriced for what is offered. Often twice the price of Economy

To which I would add that the mileage uplift over economy fares is not adequate (10% additional miles on a economy fare earning 100%). Compare that with other carriers who offer a 25% or 50% uplift for PE.

When SQ introduced PE I was interested to see what it offered, but I think it is overpriced for what it is compared to the competition. The lack of a PE toilet and a curtain do make a difference - part of what you are paying for is a separate cabin - and pre-takeoff drinks and a better food and drink service are surely not too hard or costly to offer compared to the ticket price.

I don't see the point of fitting curtains if they are then left open. Did they think at one stage that they would be closed and then decided not to bother?

I fly SQ Y to Europe to Australia 4 or more times a year, normally on W H or E fares - if discount PE was not too much more (rather than twice the price) I might choose it - or if the service was much better and the product more differentiated from Y and the miles earning higher (on SQ and partners) I might be prepared to pay a fare closer to the current PE fares.