Well yes, but doesn't it's usefulness come from the tight integration with gmail only features? disclaimer; i only used Sparrow for a bit a long time ago so perhaps they've made these features work in regular IMAP as well..
I don't know exactly the protocols behind Exchange (IMAP ? MAPI ?), but it seems to me that it is, for now, Google's prefered way of accessing emails & calendars from a mobile device (at least from iOS).
