Since yesterday's announcement that Google had released an iPhone-ready look and feel for it's Google Apps, I've been playing with GMail and Google Reader quite a bit on the iPhone. This is a much improved experience. I'm impressed. The apps are responsive and function well on the reduced real estate of the iPhone screen.
Because GMail pre-loads recent messages, clicking on a message to read it brings it up nearly instantaneously. The address fields also auto-complete. I could see myself using GMail on the iPhone instead of the built in Mail application and getting along very nicely.
Reader still isn't my favorite way to read news. I've used NetNewsWire on the Mac for a long time and have a style of reading news that Reader just doesn't seem to support. Still, it's snappy and clean on the iPhone and that's a real plus.