[isdnmatt]

I asked this same question and the overall answer was no you can't use the native SMS. What you can do, is enable Gmail push-email to sync with your email and have GV SMSes forwarded to your email. Then when you get a new SMS from Google Voice, it gets pushed to the native email program. Then you can reply just as you would as a txt and it'll get sent to the person you're replying to as a text.

I used this for the past month while I was in italy to avoid texting charges. I disabled save sent messages and include message in reply to speed up the process and reduce clutter.