As you are probably already aware, the T-Mobile G1 features Push Gmail. As mentioned above, the G1 only asks that you enter your Gmail login credentials in order to setup your device to accept push Gmail emails.
The Push Gmail feature, as many BlackBerry Email and Microsoft Exchange users will likely attest to, is invaluable for staying on top of all your important emails. Even if you don’t rely on time-sensitive emails, it’s nice to have emails pushed directly to you handset without having to affect an email update (as with POP3 and IMAP email solutions).
Setting up other email accounts is just a matter of entering your email address and your password. The Android OS email client automatically configures your email account (downloading your Inbox with folder structure intact) and should be up and running in no time.
Push Gmail seems to only work with the main Gmail account, additional Gmail email accounts don’t have push functionality enabled.
Full-HTML emails are fully supported and parsed quickly. You won’t have to wait to load images (especially over the 3G connection) in your emails allowing you to enjoy HTML formatted emails.
Text messages are easy to send. The “Messaging” application threads SMS text message conversations, which is a huge plus for heavy texters. You can manage your text messages as conversations between contacts, and even send out mass messages to your entire contacts list (again, automatically synchronized with Google Contacts).
Google Maps, YouTube, Web Browser…..