A WebmasterWorld thread complains that the AdWords management interface at adwords.google.com does not rendered on the iPhone (and possible Android). In fact, I tried it and it booted me out after several seconds. I managed to take a screen shot of the page trying to load.
In addition, if you try to use the AdWords interface with Safari 4.0, Apple's latest release of their browser, you get the following message:
Support for Safari 4 is coming soon. Until then, please use an earlier version of Safari when viewing the new interface.
AdWordsAdvisor did comment specifically about a mobile AdWords interface. Let me quote what the Google representative said:
This is understood to be very important, Kobayashi, and though I can not predict a timeline (mainly since I don't know it) I do know this is being worked on.
So it seems like a mobile version of the AdWords interface is coming in the future. When exactly is the million dollar question.
Forum discussion at WebmasterWorld.