Remote Access gives you live two-way communications with the HD DVR. You can check to see what you have available to watch and even delete recorded programs.
You can edit existing "timers" to adjust priority, padding (both front and back) and the number of episodes to stack up.
You can review conflicts or just see what's scheduled as well as skipping individual episodes without editing the timer. I use the skip feature a lot during the summer months when the guide data seems to go stupid.
If you have a Slingbox and the web viewing software, you can even watch live or recorded content from your DVR through the same interface.
You must have the HD DVR reachable from the Internet to use these features. The Sling service doesn't work with devices that it can't talk to so the application doesn't cover as much ground as a satellite delivery based setup.
For the supported devices it is arguably better than sitting in front of your TV with the remote.