Here's Trevor Squires talking about why he wrote Propane:
Campfire is about immediacy. When you want to share a file, you just upload it. Seen a cool image? Copy in the url and Campfire shows it inline.
With Propane I'm trying to take immediacy and turn it up to eleven. In a desktop app I can do stuff that a web app can't do.
When you drag an image from Safari and drop it into Propane, what are you trying to communicate? Sure, Campfire displays the image, but where did it come from? How many times have you been asked "where's that from?". Propane does that for you.
Same thing with text from a web page.
When you copy in a tweet url, why are you doing that? If you want to share the tweet, the actual message is what you meant to share - not some opaque URL. Propane turns it into a twicture because that's what's recognized as a great way to share tweet messages.
How many clicks does it take to upload a file? 3? This is supposed to be immediacy. Just drop the file on Propane.
And one application's 'immediacy' should not get in the way of the same quality of other applications. That's why Propane strips out stuff from Campfire that a native client doesn't need. Navigation bar? Don't need it when you've got control of the app's menu.
When you copy text out of the transcript, did you really mean you wanted all that markup and crazy-ass "lets turn table contents into something legible"? Or did you mean to copy:
trevor: this is cool
giles: indeed it is
matt: I like turtles
Campfire is great. Propane just improves it. The "why" - immediacy - is the killer feature for me.
The fact that 'space' or any punctuation mark commits your tab completion is important to me. I thought long and hard about "what does a user intend" and tried to make Propane behave in a way that doesn't disrupt their intentions.
It's the only reason I wrote this.