I gave "Sonar" a spin and have to say that the excellent and free "fSeventer" offers all the functionality and info that most anyone would want or need.
I'm staying with FSeventer.
I used Sonar's uninstaller to delete Sonar and then then used the outstanding and free "EasyFind" to look for any files/folders that Sonar's own uninstaller might have missed.
EasyFind found 14 of them.
I then typed in Matterform, and EasyFind came up with 8 more.
Interestingly, Matterform sells an uninstaller ("Yank"); its last iteration was way back in March '07 and which has gotten some less than stellar reviews from MacUpdate reviewers.
This does not inspire confidence.