TreeBarber,
Is the 'wax' off your Velocity yet? My Velocity is farily 'young' and while I no longer notice that waxy new feel, I can't help but wonder if there's just enough on the rope to make a difference with the Grigri. If your Velocity no longer has the wax on it, I'm gonna be very curious to see how it performs with the Grigri.
The thing that I like about the Grigri is I can ascend and descend with it. If I have a high entry, say 30' or more, I tend to ascend with an ascender and switch over to the Grigri when I'm in the tree and anticipate ups and downs or manuevering about the tree.
Then, since the Grigri is already 'on rope', it's convenient to rappel on and pretty much has a hands off auto-stop. But I have to go a bit slower because the Grigri does heat up.