With a bit of further analysis, it now seems that the 2.1 FW does improve THX mode in a way that may make it a perfect fit for folks without plans to calibrate. With past measurements
on my set, trying to get more brightness in THX mode by moving the Contrast to 75 resulted in a degraded Gamma at high IRE. After FW 2.1, this is much less. It provides a 46FL measured (56 FL with D-Nice's correction).
I noticed changes in THX mode after 2.1, but at default settings they were not significant enough to mention.
For rooms with dim lighting, the Custom settings for Low panel brightness provide better results than THX, with lower light output that works well in those environments.
For folks wanting higher light output, using the 2.1 patch with THX Contrast at 75 and Color bumped down to 48 or 49 is a great option.
Gotchaa, based on your knowledge of the 2.1 FW does this make sense?
THX Default after 2.1 - High Contrast.pdf 257.005859375k . file