Hi Audiodog,
Yep, I own both of them. The Woodpecker is an "active" ribbon, so it runs with phantom, and it's not really like what you expect when you think of ribbons. The Woodpecker has a real smile curve to its sound...a fairly pronounced mid scoop. While this can be nice on specific sources I use mine pretty sparingly. The R84 is the classic ribbon sound...smooth, realistic and not at all hyped on the high end. These mics are both ribbons but I wouldn't call them similar at all.
I like 'em both but if you can only get one I'd say get the 84. If you have a decent room you can set it up to capture a voice+ac.guitar recording by setting it a few feet away from the performer and moving it up or down to change the voice and guitar balance. Gives you a great kind of vintage-sounding recording. It also makes a great mono room mic for drums and can be really fantastic on E. guitar. When you first get the 84 it's going to sound dull...particularly if you A/B against a traditional LDC like an 87, but play with it a bit and you'll likely come to love it. Make sure you have a decent pre with a bunch of clean gain though.
I've used the Woodpecker on upright bass and an occasional V.O./book-on-tape guy, but not much else.
Good luck
Dean