You, and thousands of others like you are asking the same questions.
Of course you can get e-mail updated on a schedule (every fifteen minutes for example) today with Cingular and a Windows Mobile device. Push e-mail is where e-mail is sent to your device immediately when it is sent, and that has been the chief advantage RIM has leveraged with its Blackberrys.
One obvious advantage is that as a Microsoft application, we can assume Microsoft's push-emial will better integrate, and increasingly integrate, with their other services and offerings.
If you work in a corporate environment, it may be a good idea to talk to your IT department to understand what plans they are making for integrating Microsoft mobile e-mail. Or maybe they are looking at other vendors like
Visto,
Good,
Seven,
Intellisync or even
Funambol's Open Source solutions.
Also, click here to learn more about Microsoft's recent partnership deals with Cingular. This is
BIG news, and probably does more to hurt RIM than its patent disputes with NTP could ever do.