It's really possible to build desktop apps with browser tech now, the holy grail for so many years. Proof is in something like Photoshop for the Web. Amazing.

Agreed! I used the File System API when building a portfolio tool that needed to handle resume uploads. The ability to read files directly in the browser without sending them to a server first was a game-changer for privacy-conscious users.

One gotcha I ran into: browser support is still spotty. Had to implement fallbacks for Firefox and Safari users (they don't fully support it yet). Ended up with a hybrid approach - File System API for Chrome/Edge, traditional file input for others.

The permission model is also interesting - users have to explicitly grant access, which builds trust but adds friction to UX. Worth it though.

What are you using it for?