We're doing a lot with VDI at the moment, especially VMware View.
One of the main challenges with VDI is the well known "boot storm" problem. This is a bit of a misnomer, as the issue is related to any simultaneous activity within many virtual desktops that causes lots of disk I/O - boot and log-in are two examples, but traditional anti-virus updates, log off and other activities can also generate problematic loads.
The solution here is faster storage. However, managing this with traditional storage arrays is not always the best way forward as it can become expensive. Also array-based flash acceleration solutions usually only accelerate reads and not writes, and VDI traffic is notoriously write-heavy.
What we therefore need is either an all-flash array or tiered storage including flash (many exist) and some fast interconnects, or some host-based flash. All-flash arrays or tiered storage are great where budget allows, but we often see clients looking to manage virtual desktop performance at best cost without re-inventing their back-end storage.
We've therefore considered several host-side solutions for clients, and we very much like Atlantis ILIO. This is because it uses RAM rather than flash as the underlying storage, which has better performance and long-term durability characteristics.
We're currently deploying ILIO for production, non-persistent VDI workloads in several client environments, as well as pilot setups for others, and it lives up to it's promise - it is fast.