Do any rc planes have programmable esc's. I know with some rc trucks you can program whatever percent total throttle or change how the truck accelerates.

You can use the EPA on the radio to limit the throttle, enable the slow start feature. What is it exactly you need the ESC to do?


Buzz.

Here's an example of a rc truck with an esc that you can program.
http://www.youtube.com/watch?v=lscQaM7Oqm4

When I fly a helicopter with my DX6i I can adjust the throttle curve, why can't I do that with an rc plane?

you can unfortunately not with a DX6... you'd need to step up to a DX7S or better.

Almost all ESC's ARE programmable. They vary greatly on what you can or cannot change.