The biggest problems faced by the two consultingware shops I've worked at, is that they thought they were product based shops and every design desision reflected that. But the product became so complicated that every client had there own special configuration and no-one really understood them all at the same time. It became very common to make a change for one client and break a feature for someone else when they upgraded.

IMO they would have been much better off to embrace consultingware and plan for it.