Well I have good news and bad news to report. The Vello grip does NOT work with the ENL3 battery. I reached back out to BHPHOTO who originally told me it was compatible with the D700 and now they say I was given bad information. They suggested a different off brand ZENBG300 which is out of stock.
So, I did some digging on the new ZEN recommendation and found on Amazon lots of positive feedback on the item, however, an equal number of negative feedback. Its really weird, lots of happy customers with D700's and many unhappy ones with the very same issue, ENL battery not recognized.
In my case, as soon as I connect the grip to the D700, if it has an ENL battery in it, the camera indicates DEAD Battery and will not work. Soon as I disconnect it - or put in AA, everything is fine.
I guess I have a decision to make about a return and spending an additional $180 some odd for the nikon grip. T
Tom Trujillo The CUBAN NIKONIAN! D700, D70s, F5, N70, 8008, F-PhotoT
"Nikonians membership - My most important photographic investment, after the camera"