FWIW I've take the lid off of 3 CPU's. 1 3700+ 754, 1 3400+ 754 and 1 3000 754. I won't be taking the lid off of any more CPU's.
The temps are about 2-4C lower under load with the TDX.
The TDX can not and will not put enough pressure over the core side to side 90 deg from the screw/mounts. The TDX rocks on the CPU causing hot spots from poor contact. This happened on the 3400+ and the 3700+ for me. The cores are not flat.
The lid protects the core and does so very well.
The TDX hits the cam box in most conditions.
The resell value of your CPUs will tank. You'll just about have to give it away.
If you ever try to make a sandwich back out of the lid and CPU, ALL of the epoxy material must be removed from the CPU and the lid.
If you want better temps, get a MCW6000 or 6002. The Swiftech was about 20% better for me over all then the TDX. I hated the TDX 64.