Are there downsides to 0% Financing?
For cars, there are usually not the same gotchyas in the contract to 0% financing that things like furniture/TVs have.
But, the major gotchya is that, in general, to get 0% financing you're likely paying a high price for a brand-new depreciating product.
Consider the fact that you'll only find commercially available (as opposed to a loan from a family member) 0% financing with high-markup depreciating material goods like cars/furniture/TVs.
That, in and of itself, should give the guidance.
You can't finance houses for 0% to live in or rent out; you can't borrow on margin in a stock account for 0%; you can't get a business loan for 0%.
Essentially, if you want to purchase a brand new vehicle and you can negotiate a reasonable deal which includes 0% financing, nothing wrong with it.
But, you might have been able to negotiate a better overall deal with a different interest rate, you might have been able to buy an equivalent car a few years old and saved money, etc.
In this forum there would be general consensus that getting the 0% wasn't dumb; rather, the dumb move was buying a brand new SUV and thinking you were smart.