Google IMAP and the Mail Application
The Post Office Protocol (POP) mail retrieval method just doesn't cut it these days. People want their mail to appear in sync on all of their devices. Login using your favorite mail application on your computer or with the iPhone or web mail when remote. Email shouldn't be something that needs to be managed on each device!
Since Google added support for Internet Messaging Access Protocol (IMAP) to Gmail I check my mail more frequently. This is because I am not dreading having to login to the web interface to perform clean up work.
Now that having mail on multiple devices is pain free, I use the Mail application more often. I no longer visit the Gmail site when at my home computer (this is probably not a great thing for Google since I am not viewing the ads on their site). The Mail application handles multiple IMAP accounts flawlessly. The speed is great and the interface makes reading and writing messages easy.
Another great thing about using the Mail application again is that I can access my Mac address book. I would utilize the Notes and To Do features if they would sync to matching applications on the iPhone. If Apple doesn't add this feature maybe a third party will develop a solution after an SDK is released in February!
Overwhelmed by your mail? Here is a great Google Tech Talk with Merlin Mann of 43folders.com titled Inbox Zero where he discusses the struggles associated with receiving high volumes of email.
What the elf happened to applehound? We're waiting patiently for some new info :)