printbite last at least as long as your printer. I had one of the first sheets - actually outlasted the printer, which is currenty on ashelf awaiting the day i get a larger workshop and can be arsed to replace, what i believes is a dodgy stepper driver.

The sheet on the delta has been going strong for over 2 years now.
The current sheets are about half a mm, but really really hard. I've actually removed mymat nylon with a hammer and chisel. Didn't mark the printbite. So never use mymat nylon with printbite !
You can also get any graphic you like printed on the current version.
Heat transfer is 100% - I've sused my ir thermo and what it reads is what it says on the printer control panel.

Currently using stick sheets from lankeda.com on the knp and the i3. Good stuff but you have to really dial in your z offset/calibration and up the first layer speed till you're on he edge f not sticking. Otherwise removing prints is bloody difficult.
No idea what it is. Doesn't look or feellike buildtak and is also seriously tough
But it's good for all that.
And it was free :-)

And a quick wipe over with magigoo every 3-4 months stops the worst of the over-stick.