I have made an attempt with it. Was not a fan. Mainly cuz I just sucked with it.
I have seen other people using it with great results.
If you do decide to use a hot knife, make sure you take all the safety precautions. A well ventilated room and a respirator with that proper filter cartridges. A hot knife melts the foam, not cut. So you don't want to be breathing that stuff in.