Let your gut be your guide. And if your feedback involves a big issue, something the person you're working with really needs to take seriously, then find an appropriate time and place - even if it delays the session. Don't give important feedback in the hallway. It's a mistake to blame all the problems with performance reviews on the people who deliver them. Feedback is no different from any other business process - you get out of it only what you put into it.
People are responsible for their own performance.
There's feedback all around you - if you pay attention. Saunier offers an example from her own experience. She heard from a unit coach that a new employee, who'd been on the job three months and had been working with Saunier on a project, complained that he wasn't receiving enough feedback. We walked back together from the client's office every day. And every day we discussed what we could do better.