Keynote is the best presentation software that I've had the pleasure to use. It was one of the major drivers behind my first PowerBook purchase in 2003, and I continue to use it for preference - to the extent of when forced to use PowerPoint I'll either chose not to speak, or will prepare slides in Keynote then export images and use them to construct PowerPoint slides.
It's been even better since I got an iPad - a supremely excellent portable presentation tool.
My workflow has been to prepare a presentation in Keynote for Mac, then transfer the files to the iPad, originally via iWork.com and now via iCloud. Having to go through the websites has been slightly clunky, so the update of Keynote (both the Mac and iOS versions) put out today offered some streamlining.
Unfortunately, files for the two platforms aren't directly compatible - which means that the promise of change a file on the Mac and have it replicated on the iPad just doesn't work. It's not safe to have the same presentation open on two devices - the additional conversion needed to move the Mac file to the iPad means those changes just don't flow the way they should.
I guess there's a wait for iOS 6 and iWork 'XX to get this working properly.