it is a horrible experience. It is not worth to pre-purchased the ticket at all. There is no separated line for people have tickets. We still have to stand in line with people without ticket to redeem the tickets. The line is over 2 hours long, we gave up, just wasted our tickets. This is nothing to do with Viator, hope Viator can give the feedback to The Peak Tram.
Based on my experience, don't bother buying a voucher assuming that the entry would be quicker. When we went, due to holiday Christmas, there was a huge crowd for this activity and we had to stand in the queue for around 90 min. They were selling the tickets for fast lane entry with couple of bucks extra which would be better to Opt rather than waiting in the queue with a voucher.
Over 2.5 hours in a line to get on the tram and an hour to get back down. Place was packed and view was very restricted.
Of all the things we did in HK, this was by far the worst.
If you must do the trip, avoid the dusk trip at all costs.
The views were beautiful. Be sure to go to the top of the observation building and listen to the recorded narrative. We were surprised that the voucher only included one way on the tram, so be sure to buy round trip fare - it is a long walk.