If they ask, they either think they have a good one and what to hear it, or they are new and would like to know if they made the right choice. I approach it as they want to know if they made the right choice, I try and tell them the strengths, weakness, if the strengths out weigh the weaknesses and what they might want to look for in their next selection. Telling them their good, bad or OK doesn't really help if you don't break it down. JMO
I try and be direct and non-punishing, a concept some on here have a little difficulty with some of the time.