The most valuable feature is the no-forklift upgrade. While the thing is running, I can change out the controllers one at a time and keep the customer up and running. I can add shelves and storage and SSD drives or spinning drives to the system, while it's running. I can bring all that in and rebalance the load across the new disks or, if we take disks away, rebalance the load across what's remaining, and it just works. Also, in terms of auto-tieriing, Compellent writes all of its writes into Tier 1, unless of course you do something silly and pin a whole bunch of LUNS, which means you're telling your VM, your data stores, that they have to live in that top-tier storage. As long as you follow the best practices recommendations and let it do its own auto-tiering then it works very well. In most cases the customers with all-flash, most of their active data lives in flash. So, they're really using all of those IOPS and performance in that tier, and the other tier or tiers are just being used for cold data storage. It works very well, as long as customers follow the best practices there.
