I read a pretty interesting posting from Matthew Miller, ZDNet's Mobile Gadgeteer about threats to RIM's dominance int he business market. Here are two key paragraphs:

People may say that BlackBerry devices are reliable and their email always just works. I have been using Windows Mobile devices for years and for the last three I have to say that my Windows Mobile Standard/Smartphone (non-touch screen) devices have been ROCK SOLID. I currently have a hosted Exchange account with 4Smartphone that is great for keeping all my devices in sync. I have only been using a BlackBerry Curve for a couple of months and I have experienced two complete lockups for no apparent reason, compared to zero lockups on my T-Mobile Shadow since I bought it last fall. I think the argument for reliability is one made by people who have not had personal experience with both platforms. Either that or I am one very lucky user.

Security has also been a strength of RIM devices, but I think Microsoft now has those same security features available in Exchange ActiveSync and Windows Mobile.

For the full article: http://blogs.zdnet.com/mobile-gadgeteer/?p=1034#more-1034