I'm also in a non-trivial tax situation, GPT Sol did better than my specialist accountant this year. It needed a lot of steering from me and about 2B tokens, but that is better than spending $3-4k in preparation fees. Total time to prepare and handle steering was still less than I normally spend on tax prep with my accountant.

I think what helped is giving it 100+ pdf and csv documents of my full situation so it knew everything about me and could cross-reference with all my bank statements.

So, GPT Sol outputted tax return PDFs that you were able to submit to the IRS? (I'd imagine that you couldn't directly e-file like you could from TurboTax.)