According to the Maui News, the Hawaii Superferry filed the schedule and fare documentation with the state Public Utilities Commission.  Here are the key points from the filing:

For passengers traveling from Honolulu to Maui/Kauai routes, the one-way ticket for an adult will be $51.80 on off-peak dates and $61.74 on peak dates.

For the passenger traveling from Maui to Honolulu, the ticket prices are $51.54 off-peak and $61.42 on peak dates.

For a family taking a vehicle from Honolulu to Maui, the ticket price for a passenger car up to 17 feet long will be $58.88 on off-peak dates and $68.82 on peak dates.

On the trip from Maui to Honolulu, prices are $58.58 off-peak and $68.46 on peak dates.

In general, peak days are weekends and holidays.  Peak dates will be announced at the beginning of each year.  

The schedule is posted on the Hawaii Superferry web site.  Maui/Oahu service will operate in the mornings to early afternoon.  Kauai/Oahu routes will operate in the late afternoon and evening.  The schedule is not conducive for day trip island hopping.  Travel time will take 3 hours.  As previously reported, the service is schedule to begin in July.