The first time is the best. Consider this as a kind of transportation, not an attraction. If you need to go to Pudong from the bund, this is the way to go. Only other way is by taxi and it will take you on a detour to the next bridge or the tunnel. If you want to see the Pearl tower, this ride will take you very close.
I would describe it as a mix between a concert with Jean Michel Jarre / a carnival ride / a train ride.
I always use the tunnel to get to Pudong, if I'm already at the bund. At night time it can be hard to find a taxi in Pudong, that want to take you back to the bund, so the tunnel is easy and takes about 5-8 min. During tourist season, it can be crowded in the weekend, but usually you only need to wait a few minutes.
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