I am using the Thunderbolt-->FW adapter, and it is very stable, and it may be even faster than the strait firewire 800 connection I had on my previous MBP. Again, this could be attributable entirely to the new faster MBP Retina that I am now using. Either way, nothing to lose with the adapter. All of this is in the context of tethered shooting with an IQ180.
For downloading from CF, I use a FW800 via the thunderbolt adapter, and it works fine.
I'm sure a native TB reader maybe faster, but not sure of what that will be a game changer in any sense.