When it comes to describing our level of familiarity with something or someone, "well-acquainted with" definitely gets the job done. However, if you want to spice up your language and expand your vocabulary, there are plenty of great synonyms to choose from. For example, you could say you're "familiar," "versed," or "conversant" in a subject. You might describe yourself as "adept," "proficient," or "skilled" in a particular area. You could also use "knowledgeable," "well-versed," or "well-informed" to describe your level of understanding. Ultimately, the choice of synonym will depend on the situation and the audience, but by exploring new language options, you can craft more nuanced and impactful statements.