Nifty as hell. Finally something to replace that stupid and complicated buildcd/stripiso combo.
I'm wondering about the XA support as well.
Things I'd like:
Config file support that lets you order the files and directories on the disc (in a hack, I'd prefer to keep the files in their original physical order), maybe also have an option to specify starting LBA for each file, specifically for those rare games (like Vagrant Story) that are empty in the middle of the disc.
Dump support-- take a disc or ISO image and dump the contents into a directory, and takes measures to extract XA data properly.
A library so that I (and perhaps others) could implement its functionality into a custom patcher.
PS- I would love it if you could write a similar tool for PS2 DVD.