An easy to install and very useable guestbook. Any questions I had were were already asked and answered on the Phoca forum and it's nice to see that the developer is active on the forum and replies to queries.
The only reason I didn't give this maximum points is that within two days of my guestbook going up I got a lot of spam and feedback from some (would be) posters (friends) complained it was initially difficult to understand what the math captcha was.
In summary, this is a good guestbook. I'll post my feedback to the developer and, as he seems to take great pride in his work, I'm sure the next version will be even better.