Like I just told support, I would like to see hazel use NC over growl.
I have 6 apps that use growl. Dropbox,hazel, Skype, transmission, tvshowhelper and gfxcardstatus.
I use them along with an app called hiss that is able to foward growl notifications to NC. But they all appear in the same list, under the same app name and with the same limit of messages. Basically, it gets really crowded really fast, and I'm not always able to see all of my missed notifications since the limit is 20 recent items. Also, I am not able to click on the notification to access the specified app.
I personally don't care how that switch is achieved.. Whether its using some kind of hack, a forced change for everyone or an option in the preferences, so I would be fine with a hidden default.