Out of my 4 bikes only one, my Mongoose Amplifier 2, still has a triple chainring. Single or dual appealed to me because I never use extreme high or lows. My On-One Summer Season is 1x9 using Funn Hooka crank and a single 36 chainring. My Mongoose Deuce Pro is 2x9 using Truvativ Holzfeller 36-24 crankset. I have just fitted an FSA K-Force Light Carbon cranks with 39-27 to my Giant Anthem. This last one is the best and really suits me, I don't miss the extremes at all. 1x9 is ok for me when there's not much in the way of hills around, up or down. With the 2x9 36-24 I sometimes miss a little more high gear on the downs but manage ok. The 2x9 39-27 remedies this just right. I have 11-34 casette on all three bikes. I won't go back to 3x9 anytime.
Also 2x9 was easy to set up on both bikes using existing front shifters and mech using the limit adjusters on the front mech on both Deore on the Mongoose and XT on the Giant.