I have used it quite a fair bit when I was working full-time on my mental health during a retreat.
I sometimes have resistance to using it. Mostly, when the negative belief that I wanted to counteract was pretty big, exploring the underlying issue using focusing, Internal Family Systems therapy, or some other introspective technique seems more useful in that situation.
This concern seems legitimate to me. There is often important information in negative feelings which I mostly explore with Focusing or Internal Family Systems. When my brain thinks that there is still information in that feeling but I am nevertheless applying the HEAL method, it can feel as if I am convincing myself or, as you said, repressing your emotion. That seems indeed somewhat tricky to me.
However, I also think that there is not always useful information in negative feelings. I often had times where I already explored the negative feeling or knew where it came from but it still came back. Before having heard of HEAL and reading Rick Hanson’s material I thought that you always had to fully experience and feel a negative feeling in order to overcome it. I no longer think this is the case, instead I replace it with thoughts or behaviors that are more helpful and in these behaviors also incorporate the useful bits of what the negative feeling tries to achieve.