There is nothing inherently bad in the decision. What would matter is on what terms did you and your partner agreed prior to the trial separation.
Any new relationship feels excited as you learn about your new partner. With time though, the in love stage wears off and you find yourself in more of a predictable routine as the two of you get comfortable with one another. It may be those two things that you're comparing b/w your husband and this new man.
Before making any big decisions, give it some time, think about the pros and cons of a divorce, what the trial separation is supposed to accomplish and what you really want in the long term, whether with this man, your husband or someone else.