I think there are a lot of benefits to a web app here including:

  - Cross-platform support
  - Collaboration and sharing, especially with unregistered users
  - Speed to get off the ground as a new user
  - Automatic updates for fixes + features
  - Integrated live support
  - Great open-source community

The largest downside for me is less robust offline support, but that's improving. I'd be curious what the most important missing pieces are for you. Would love to minimize those downsides!