Overall it is a robust BI platform that is not difficult for a technically-oriented person to learn and use.
I am a huge fan of Analysis Services and actively try to find ways to get data into cubes for reporting. While learning MDX may be one of the more difficult aspects of MS BI, it is powerful and anyone who has prior experience using T-SQL alone to build complex reports can appreciate its power.
I have been disappointed in how all the front-end delivery tools have been centered around Excel and SharePoint. I understand it from a business sense but I much preferred the ProClarity interface as a stand-alone ad-hoc reporting tool. Many end-users are intimidated by merely mentioning pivot tables and therefore do not even try to create their own queries.
As Microsoft Gold partners, we had access to the software already and have enjoyed success with a very small implementation. As this grows we may look toward additional delivery options but not the base data warehouse system.
Yes, the product was fairly easy to learn without training. There are some professionals that could use this approach as well depending on their learning styles. With all the information available, I generally recommend this approach.