When expressing gratitude or acknowledging someone's efforts, the phrase "be appreciative of" can be replaced by various synonyms. One such synonym is "acknowledge," which means to accept or recognize someone's contribution or effort. "Recognize" can also be used in this context, meaning to identify and take note of someone's efforts or contributions. Additionally, the term "thankful" is a popular synonym for the phrase as well, which emphasizes gratitude and appreciation. Another synonym is "grateful," which has a similar meaning and conveys a sense of indebtedness and appreciation. Ultimately, there are many ways to express gratitude and appreciation, and each word carries its own nuances and implications.