There's a recent Trip Report on the Jet Quay service either in the Trip Reports forum of FlyerTalk or on SQtalk. Remember, though, customs and immigration are very fast at Changi. The moving-walkway-assisted stroll to customs, even if far, will consume the time it will take for your bags to reach the belt. Jet Quay service probably will not save much time. I'd say do it for the VIP treatment and spoiling, if you like.