7D + Vello BG-C2 + Aftermarket Batteries = Trouble?

I'm looking to add a grip to my 7D and while I'm looking for a deal on a used OEM it seems likely that I'll end up with a Vello. I've been reading a lot of accounts of most aftermarket batteries not working with the Vello though.

Was this a problem with the initial release of the grip and batteries, and is it on going to this day? Or has the problem been solved with later releases of the Vello grip and or by the aftermarket battery producers?

I have the Vello grip on my 7d but I am using canon batteries only. I am interested in what other people say about this because I have been thinking about getting some 3rd party batteries