Microsoft creates and manages COM and DCOM, so there is only one basic, compatible implementation. But through OMG's efforts, most incompatibilities have been resolved. The IDL level is where differences begin to show up. DCOM doesn't manage errors at the IDL level. Choosing and implementing an enterprise middleware strategy is probably the most complex task any systems department will ever face.
Remote administration is vital for large installations.
The middleware must support not only your data but also all your database management tools. Scripting control is vital. Focus more on what you plan to do in the future than what you do now. EJB is another distributed object system. If you believe the hype, the Extensible Markup Language is the answer to all such problems.