Hi,
In my career, I have participate in several ERP implementations with different roles: user, key user, developer, BPM and DBA. Those implementations have different level of customizations. In fact, my personal believe is that every ERP needs some software customizations to fit in a specific industry, due to, the functionallity out of the box, of any ERP, can´t cover all the processes. With more specialized or focused industry, the more software customizations will be required.
From the point of view of the final user, you will ask for a customization that make all your process with the click of a button. The classical phrase that I heard is: What is the gain, in terms of effort or amount of work, of changing the system? And it is valid, due to, in fact in general, it will be more work to do for the same process.
From the point of view of the IT, the less level of customizations, the better. This is due to a hevily customized system will require extra support contracts to keep the customizations under maintenance in the case of the need of technical support. Plus if you need to perform a migration to new releases of the product, it will be easier with a small number of customizations. I know company cases that prefeer to stay in older versions of their ERP due to the complexity to migrate.
A rule of thumb, stats that, if you perform more than 30% of customizations, the chances of a failure in the implementation, raises to double.
In conclusion, if we talk in terms of success ratio, It is better to customize processes than software. This not means that you will avoid software customizations, but you will need a thight control over them. Another rule of thumb, is: if the software customization, add value to the process, then proceed.
Miguel.