What's new in arc3?

Ay, please let's not start. Arc is still in development. I've never made any claims for the current version except that it works reasonably well for basic web apps.

"Are we supposed to think Arc is a pragmatic language for shipping production applications"

No.

pg is designing the language right now. It's not being polished; being readied to build twitter on top of. The important thing right now is the actual design of the language, not all the random helper functions. They can easily be added in later. If you're going to build a production application on top of arc, making sin shouldn't be much of a problem -- it won't take very long, and is one of the least of your concerns.

Not for another 94 years or so... http://www.paulgraham.com/hundred.html

The "most fundamental parts" have been around for about 50 years. It's just a matter of combining them right. They are quote, eq, car, cdr ...