Don't apologise. If they don't recognise the extraordinary value of unsolicited first impressions they will just have to learn the hard way.

For field testing my iPad apps (for instance) I will just hand them an iPad and not give them any instructions or hints on how to use it. And then I will watch intently what they do and what they don't do. Two minutes of unsullied first impression is pure gold. The only 'downside' is that occasionally you learn that you have to redesign the interface...