Tim Bray - Lightroom Fanboy:

"First of all, did I mention it’s fast?

Second, there’s no Save button. It just takes care of that. And remember, all the edits are deltas, as in non-destructive. It occurs to me to wonder why all software that edits any data in any way whatsoever doesn’t work like this.

[...] It’s really good at remembering what you just did, so you very rarely have to type in something more than once when you want to do it again."