- Printable paper backups
- Only-one-time-ever-needed backups (deterministic wallets)
- Multiple wallet interface
- Offline wallets with watching-only wallets for the online computer.
- GPU-resistant wallet encryption
- Key import & export
- Key sweeping
- Coin control
- Custom Change addresses
- Transaction history export to .csv
- Payment request blocks (to be copied into emails or webpages with URLs)
I'm sure that's not even all of it. There's been a lot of demand for a live CD with Armory on it, because thousands of people rely on the offline wallets feature, but it's not trivial to setup offline in Linux and I'm not good with live distributions (though I distribute an offline bundle for Ubuntu 10.04-32bit for that reason).