Another happy odoo user here: we use it internally for CRM, sales, purchases, accounting, product inventory. We also developped modules to make it the back end of our web/mobile shop, and of our mobile apps.

The flexibility is really great, and while I have not used other ERPs, I believe it is easier to develop for, and to use as an end-user. Part of the code is open-source, and you have access to the source of the non-free apps. As a bonus, it's Python!

Regarding the pricing, it sure is less expensive than the competitors, but the cost increases fast when you add new modules, or if you have many internal users (pricing is 100-250€ per module per year + ~250€ per internal user per year)

EDIT: a live demo with most modules installed is running at https://master.odoo.com/saas_master/demo