Soy Formula

What are the opinions on soy formula? I want to hear whatever advice/experience moms have with giving their babies soy. My son doesn't have a milk allergy to my knowledge (He's 4 months & still exclusively breastfeeding) but I'm thinking of soon supplementing with formula & I'd prefer to keep cows milk out of his diet for as long as I can. Like I said...I'm open to hearing anything anyone has to share! ☺️