HPE Oneview has come along way. When they first put it out it was next to useless. Over the years and versions, they listened to feedback and have made OneView into a truly enterprise-level robust management product. It is now a far better product than the old C7000 Blade OAs, and HP SIM. It makes management of hardware easy and makes much of the maintenance easier and safer than before. For the storage side it does a great job and is intuitive to use, but the very versatility of how you can do things can lead to issues if multiple engineers do things differently.
Managing the 3Pard Oneview will allow you to do things like reuse LUN IDs and setup multiple export groups with the same volume. This can cause performance issues, or worse. They could do a better job of protecting you from yourself...
Support and training when we implemented OneView were excellent. We haven't required any additional support since we put it in and configured it for our systems. The OneView systems have been stable through updates and HPE documentation is excellent.