I had to delid half of my E7400s for testing the core, because the TIM was so bad that the CPU would thermalthrottle under load with 1,4V and NH-D14...
I actually never cared about using the delid die mate for 775 since the PCB is extremely sturdy compaded with skylake for example, but nice to see it can also be done with the tool from roman
I have noticed gains of about ~50MHz across the board on E7400s that didn't thermalthrottle before too, so definetly worth it for chips that aren't soldered (e1x00, e2xx0, e7x00 etc)
What I wouldn't advise is delidding C2Q CPUs, i have tried it on three dead Q6600 and one two I destroyed one of the DIEs...
Here a few of my delidding experiments: C2D E6300, Xeon E5335, Opteron 6128, Pentium D 820, Pentium E5300, Pentium E2160