I’ve had a BlackBerry 8830 for a few months now. And I must admit, I’m getting over my iPhone envy. (iPhone’s still aren’t officially available in Canada!) The 8830 has the tactile keypad I’ve grown to love, a (two-dimensional) trackball in place of a (one-dimensional) thumbwheel, GPS-based mapping, etc. This means that built-in WiFi is about the only capability for which I find myself wanting.
- Integration – The BES integrates the CSD with the enterprise messaging platform (e.g., Microsoft Exchange, IBM Lotus Notes, etc.) and the rest of RIM’s BlackBerry universe. In addition to email and calendaring, this has the potential to include instant messaging (e.g., MSN, IBM Lotus Sametime, etc.) and more.
- Security – Because the BES provides a single locus of control (the BlackBerry domain), it can and has been leveraged extensively to deliver an industry leading environment for end-to-end security. Encryption, authentication, plus six levels for administrative roles, are all present.
- Policies – To quote from my review:
The BES ships with over 200 policies that can be applied variously to users, groups and devices … The ability to administer users, groups and devices with respect to policies (including software), from a single point of control (i.e., the BES server), speaks volumes to the appeal and value that this offering can deliver to corporate enterprise environments.
- Provisioning – The BES facilitates provisioning of users, groups, devices as well as associated software. Software can even be bundled and targeted to specific CSDs.
Ian Lumb's Blog 
I am freak about my BlackBerry 8300 and believe its more reliable and good as compare of iPhone. The only issue that i face with BB 8300 is to carry it.