We did this cruise this past March-April. We didn't like the Quest, we thought it was tired and very old-fashioned. Definitely our least-liked ships of all our Atlantis cruises. So much so that we probably won't do the Shanghai to Hong Kong cruise - just because it's on the Quest.
The smaller ship did have the advantage of being able to go all the way into Saigon instead of having to dock several hours away. However, after seeing Saigon, we wouldn't have minded docking at a nice small port town instead.
There were no issues whatsoever arriving into Singapore. What a great place! Of all the places we visited on this cruise, Singapore is the only place I hope to visit again.