The new Tiffen T1 IR filter arrived today (Monday). I did a few tests with various black materials I could find around the house. To make a long story short, it worked as promised. The blacks came out rich and black, no reddish/brown tint and no green vignette.
There is a half stop loss in light, but that borders on negligible. There is some very minor tweaking in post to boost the red's saturation to their previous levels before adding the T1.
IMHO, this filter helps make a great camera even better. I'm a happy camper!