I just installed the brand new Gmail for Mobile on my Motorola RAZR. In just a matter of a couple moments, I was looking at my Gmail inbox! Gmail for Mobile is a Java-applet that runs on your Java enabled phone. Keeping the network traffic down this way is a lot better option that a WAP-based email solution, which is what I had tried and abandoned previously.
Not having a QWERTY keyboard is a big limitation for smartphones especially where something heavily textual like email is concerned. Gmail for Mobile deals with this thru a clever mapping of hotkeys to the most commonly used functions (delete, in my case).
Between Google Reader, and now this Gmail for Mobile, another bit of my online existence has been sucked into the Googlesphere...and I like it!