Obviously too late for people this year, and my tax situation is relatively straightforward so I can't speak to how well it handles edge cases, but the first year I used it I went through the process with both TurboTax and FreeTaxUSA and got the exact same estimated refund.
The last straw with TurboTax was when I needed to get some details from a previous year's tax return and found out that they would not let me access a return I'd paid to file with them unless I upgraded my plan. Absolute scum. I took the opportunity to also close my Mint account (same parent company as TurboTax) which I barely use and has been sending all kinds of transaction data for them to profit from.