Processmaker works great as a zimlet, under its own tab.
1) it wipes out the mini-calendar from the left bar, no way to recover it except by disabling the processmaker zimlet.
2) everytime you click into the calendar tab and try to click on another zimbra crashes with an error message http://forum.processmaker.com/viewtopic.php?f=9&t=6410
Unfortunately only a refresh of the webpage fixes it. This was the reason why I migrated to v7 recently, however that didnt solve the issue. Unfortunately it's unusable under these circumstances, and the only way to solve the problem is to completely disable the calendar.
I couldnt afford to do that so I disabled the processmaker zimlet.
If it wasnt for these 2 issues my review would have been a solid 5.