1. found errors, e.g. where I used the incorrect exchange rate (and managed to work out how I had made that error, which I was impressed by)

2. found items which would appear to be errors except for context it did not know

3. flagged areas where it disagreed with me as to the correct tax treatment, but accepted that the law is ambiguous (and in some cases I preferred its interpretation after additional research and in other cases I did not)

4. flagged areas where it disagreed with IRS guidance, and only acknowledged said guidance after I provided links to it

5. provided highly inaccurate estimated tax calculations, and not been able to fix its estimates even when challenged

So my takeaway is that it is a very useful tool for tax, but perhaps unsurprisingly, it is not good enough to dump all your paperwork into and expect a shiny return you don't need to check. (Possibly it is if you just have a W-2 and no other substantial income, but I can't speak for that scenario.)