Cedar Point isn't open in the fall on a weekday -- after Labor Day (Sept. 1 this year) the park is closed except for Fridays, Saturdays, and Sundays. The exception would be Millennium Mania, a special, limited ticket event a few days at the beginning of September. Check out
www.cedarpoint.com for more details, and park hours.
As for right now, the crowds during the week are generally less than weekends, but if you play it right (knowing the better times to go on coasters, etc) the waits shouldn't be outstanding for anything, really.
www.guidetothepoint.com has a great "Strategy" section for how to best see the park and do everything, regardless of lines.
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Po!nt of View: A different look at Roller Coasters.
http://www.crosswinds.net/~justmayntz/thrills/