I haven't tried one. From what I have read, they are for novelty use at the seashore, or neighborhood fun, and would not normally be used for transportation anywhere (IE, they're slow). Normally called a "surrey".
Oh yeah, most of these that I've seen, only 4 people pedal- other two seats don't have pedals. That's where you put your 2-year-old.
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"be careful this rando stuff is addictive and dan's the 'pusher'."