Microsoft recently announced push e-mail support in a free update expected later this year. All the benefits of the Blackberry without the additional infrastructure deployments - all you need is a free feature pack for Exchange 2003 SP2 and a Windows Mobile 5.0 device. See the features in action here.
Of course, despite all of RIM's troubles, whether it's really a Blackberry killer all depends on the devices they bring out. If the RAZRBerry is truly a Windows mobile device, as suggested here, I have a feeling it just might.
I just hope they offer a WM 5.0 update for the SMT5600. It would be awesome if I could get rid of my Blackberry and use my Smartphone for corporate e-mail.