This is a new product, and it's usage and Gui ar by far, better than the plain S60 mailboxes experience. Been said that, there is a little feature I like a lot on my e-71 and my previous e-51. That is the text to speech.
I allows you to hear messages and e-mails (from s60 mailboxes) without reading them. It frees your eyes when you are driving or using you computer (or even better, your own phone) when you are doing something else.
With push email you are aware almost all the time that an email or more is waiting for you. And more often than before you are out of your office counting on your cellphone to do the job..., well having the eyes free is a good measure.