If you are a Gmail user with an iPhone or iPad, you should download the new native Gmail 2.0 for iOS. It has a really nice visual design and does a couple things better than the native iOS Mail app.
Just like the standard web version of Gmail on the desktop, there is a dedicated Archive button right on each message. One of my biggest frustrations with Apple Mail is that when I want to archive a message (which I've already automatically tagged with a filter when it arrived), I have to choose the "move" navigation and then sort through folders to choose the folder/tag that this message already has already been given on Gmail's servers.
Threaded messages are displayed the same way they are on the Gmail web interface. I'm so used to this as it allows me to just view the whole thing in one fell swoop instead of opening each individual message separately to find the content I'm looking for.
Search is awesome. I'm not sure why the Apple mail app can't seem to actually search the Gmail server, but it can't. I easily pulled up a receipt from almost 3 years ago that I've never been able to retrieve using the native Mail app. I love this.
The push notifications are solid and I'm now using it for all my Gmail accounts.