If your N400 is "placed in line for interview scheduling", does it mean there are no issues?

Received IL in mail, interview on 01/23/2014. Wife has early in the day and husband has it later same day.

How long does a typical interview takes? Have to make plans for baby sitting in case it takes longer.
 
The interview itself is typically only 15-20 minutes, but waiting before the interview could be much longer than that. I waited for about 30 minutes, but others have reported waiting as long as 2 hours.
 
Top