Yes, I've had the same issues with GPU Tweak. Very often (almost never after a reboot), my selected profile was not correctly applied.
Twice while gaming I ran into the issue that the fan did not come out of passive mode at all (or turned itself off for some reason), until the card fail-safe/throttle suddenly kicked in, blasting the fan at 100%.
I've switched to MSI Afterburner now, and while I haven't done any gaming yet it seems more stable. In fact I've been purposely underclocking to keep the card cool/quiet when watching movies while using graphics card functions (madVR) but that works as you'd expect with MSI, which it did not with GPU Tweak.