I actually use Ledger for a consulting business, together with Emacs ledger-mode and FreshBooks for invoicing. For taxes, I just make sure that my expense categories correspond to those used by the IRS, run a report, and copy about 20 numbers over to the tax forms.
If I want to review something with my accountant, I just sit down and read the text file with him. Of course, everything is kept in version control, and I can add comments in the main ledger file.
The Ruby scripts download CSV data from my bank and Freshbooks, and convert it into raw ledger files.
Curiously, the whole system is actually pretty quick and painless — I spend a few hours each quarter on bookkeeping, and I can automate any annoyances with a 20-line script that munges text files. You'd think a GUI would be easier, but really, there's a lot to be said for plain text once you want to automate something. And it's nice to have a big comment at the top of the ledger explaining the relevant IRS rules.