The new version is pretty usable. The author fixed the issue of slider feedback, so it’s possible to be precise about how many dice you’re rolling. There’s also a new feature allowing you to auto-tally rolls equal to or higher than a target number. Finally, you can double-tap dice to hold them and reroll the unheld dice, which is cute.
At this point I’d say THAC0 is a good choice for die pool games, and D20 Dice remains optimal for other uses. I’d still like to see THAC0 have some sort of display of die type so you know if you’re rolling d10s or d6s or what, but in practice you’ll usually know.