Great discussion!
espacially: What CRM for NethServer?
sounds interesting.
Odoo may be complex, but the features are all I ever searched for.
At the moment we´re using 3 Programs for accounting and Invoicing another for documentation and another for maintenance.
Thinking of what a new (small to medium) business needs nowadays would be from my point of view a SBS Server like NS7, a CRM/ ERP like Odoo and a Office WebApplication. With this you can use quite slim clients and I think more of 95% of software needs would be covered.