The BlackBerry certainly gives a superior email *delivery* experience, but that's about it. Ever try to read an HTML email on the BB - properly formatted? Essentially can't be done.
If all you need is plain text email, then more power to ya. For me, in 2010 (heck, in 2007), I need the ability to view a properly formatted HTML email.
But Gmail is pushed instantly, so no problem there. Other accounts can be either fetched at user-selectable intervals or can be polled by Gmail's servers (at about 15 minute intervals) and delivered through Gmail. For one of my non-Gmail accounts for which I desire instant push, I have my desktop at home (via IMAP and polled via idle) redirect to Gmail, which then hits my phone in seconds.