The way I see it, any CRM implementation is going to compel the business unit to buy into a whole new way of doing bidness. If you're really, really lucky - the new way will be compatible with the old way.

Siebol, Exchange, Act!, SAP, etc. Theyall require that you make your existing CRM way of doing things with the model they present. Any variance from their way results in that much less ROI for the whole implementation.

That (and the fact that I'm a developer) makes me always want tobuild a custom CRM. Buying into a third-party vendor's way of managing customer resources is already a very, very expensive process. Having one that works with your system, rather than requiring your system to work with theirs can save a lot of ka-ching.

Of course, using any automated CRM system is going to require that you bring structure to systems (sales & mktg.) that may not have much inherrant(sp?) structure.