Let me have a think through past instillations:
Sub Terra - rushed, awful first product to open on first day
Thirteen - rushed, poor first half of the season (if not a little longer)
Rita - had a poor first season and opened later on
Air - first season was appalling
I think only Nemesis and Oblivion are the stand out major attractions that were ok come opening, nemesis wasnt new technology and Oblivion had a very long construction timetable.
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I hate half completed efforts and its one of my biggest criticisms of Alton. Yes they can meet a deadline but at the cost of a fully finished experience. For guests that visit once a season and might go for the new ride opening what is that displaying to them?
Also while as enthusiasts we might know there is more coming the general public don't they get a ride where perhaps the hardware is working, but there are thematic elements missing and the ride hasnt had a chance to settle in properly and the staff to get used to it.
Id sooner they wait and advertise it as a late opening, using the time to advertise it more on park and offer the bounce back tickets as an option to come back and ride it, to get more people to return.
I'm hoping I'll be surprised and it will open, fully working, themed and completed in March - but history and personal experience tell me not to get my hopes up.