money saved per 1 hour (by using a 23 W CFL vs. a 100W conventional):
(77 W) (1 hr) (1 kW / 1000 W) (0.055 dollars / KWh) = 0.00423 dollars
Therefore, as you said, it would take ~236 hours to save one dollar.
Cost of 100w incandescent equivalent CF approx = $1.00
Power consumption of CF bulb = 23W
Cost per kilowatt hour (local) = $.055
Hours of use to save 1 KW = 1000 / (100 - 23) = 13.0 hours
KWh to save $1 = 1.00 / .055 = 18.2
Hours to break even (recover cost of CF bulb) = 18.2 * 13.0 = 236.6
Assuming a bulb was used 4 hours per day then
Days to recover cost of CF = 236.6 / 4 = 59 days (i.e. approx 2 months)
Mileage may vary based on local rates, but, not enough to make a difference. In fact, I would guess that in many cases the break even period would be even lower.