There is HUGE opportunity in this market and I believe one big reason is that a new generation of userbase will expect and demand a better UX than any current offering.
In fact, I suggest a great startup idea would be a to take the openerp codebase and wrap a new UI/UX around it starting with one vertical ("niche") market and working out from there. (i.e. "A beautiful ERP for medium-sized businesses focusing on your growing warehouse, sales and purchasing needs built on the solid foundation of openERP."). Not saying it would be easy, but just worthwhile. I have a feeling the Odoo rebranding points to an effort for a UI overhaul which acknowledges the opportunity of a great UX.