I'd stick with Formula+ as it's what H-D recommends, it works well, and the price isn't bad.
My kid rides an '07 883 Custom and when the dealer serviced it at the 1000 mile checkup they put Formula+ in it. I just did an oil change on it a few days ago and I used Formula+ as well. Clutch engagement and shifting all seem to be excellent with this oil, so that's what we'll stick with.
I would strongly recommend changing the primary/tranny oil with every oil change (or at 5k miles) since it's not filtered and the tranny has a tendency to shear down oil.
It only takes 1 qt., so the cost is minimal... :s
(BTW- I've tried various oils in the primaries of our two Twin Cams and have settled on F+ as it provides the best clutch feel in both. It's pretty good stuff for the primary!)