My boss does this anytime he's hiring. We have a small office and have to work together as a team, so it's important that everyone is a good fit (we've seen just HOW important that is when a poor fit has been hired).
Usually, he will just give me a heads up that a candidate is coming in and after he's done interviewing them, he'll send them over to me.
I use it more as a chance for them to ask me questions about the work culture, environment, job requirements etc -- because I feel you can gain a lot of insight into their work ethic and personailty by seeing what questions they ask and what is important to them.
I always give my boss honest feedback, but it's usually little more than whether or not I think they will mesh well with our office culture and team environment.