XtremIO was originally purchased to provide a high-performance storage platform for our critical systems. It is being used across the entire organization as a storage option in our VMWare environment for high-performance datastores. We also use it for some FC attached storage for our physical servers which run AIX.
XtremIO would be useful for any production storage environment, or even any staging or development environment where performance mattered. It would not be ideal to use for backup storage.
At the time the EMC was selected due to the existing relationship with EMC and the maturity of their product compared to the other vendor's options. However now that the maturity gap has been closed and the storage wars have proven which companies will remain for the foreseeable future, we have decided to move away from the XtremIO and go with an alternate storage company due to the price and cost of ongoing support. The EMC product is still a great product, I just find it too expensive to purchase and maintain in today's competitive marketplace.
This was one area of real disappointment. EMC support was very slow to schedule work like installations and upgrades. Break/fix support was fairly standard. After the Dell merger, things have started improving but there is a lot left to be desired here.