Raul-7,
To my knowledge, most plants
are root feeders for many major nutrients. Therefore, use of substrate heat is potentially beneficial to most plants. I mainly use laterite and gravel, so that may go along with what you are saying. As I said, it's up to the aquarist. I see lots of great tanks here, and judging by the responses I see regarding heat cables, heat cables aren't in widespread use.
When the roots become entangled, I've never had a problem teasing them off or just snipping them. Bunch plants are about the only ones I ever need to pull and replant and their roots are easily dealt with. There's no need to be careful with them IMO, because when they are pulled, the bottoms are cut anyway. In the rare event of replanting a sword, it may present an issue, but hasn't been a problem for me. The problem lies within trying to replant it without cutting roots and digging up a chunk of substrate. Crypts IME, don't have the umbers of roots to pose much problem - and I try not to ever pull them anyway.
With 3+" of substrate, I have never had to worry about my cables becoming exposed. It does require caution, though.