Forum OpenACS Q&A: Response to What does "Enterprise Class" mean?
Migrating a desktop application to a web application certainly exposes the differences between non-enterprise and enterprise. The shift implies that dedicated hardware will be chosen, it will be run 24x7, it will be backed up, it will be secure, and professional services for installation/support/training will be available. During installation, the system will have to be configured to receive automated data feeds from other enterprise systems (mostly ERP).
All of the above means that the decision to purchase ideally involves IT signing off on the technical competency or appropriateness of the solution, as opposed to before-enterprise when the department head just wrote a check. The sales cycle thus becomes much longer.
Enterprises (the kind that buy "enterprise" solutions) have too many complex systems to master each one and will rely on professional services to do this. This hand-holding is absolutely necessary for them. It costs a lot, and it's worth it.
My friend's company is small, and may have to get most of the above by partnering or setting up a VAR network. Or getting some VC and staffing up.