Sorry - missed those two. Virsto allows VMware (now) to place blocks across whatever internal/external storage exists in a vSphere environment - useful for sure, but not anything special for VDI - better for utilizing all the resources in your environment (at the cost of a lot of duplication of data around the environment to remove the possibility of downtime).
Atlantis is awesome for stateless VDI - when your users all don't care too much about their profile - think tellers/call center support people/etc. They just released a stateful version of ILIO, but at quite the hardware cost - an extra server for every 500 or so users (or if you're a SMB, an extra server for anything under 500 users), plus extra RAM necessary in each and every server to host their ILIO, plus a SSD/Flash card. We allow the same level of availability at similar speeds without all that extra cost by deduplicating straight to SSD/flash - no memory or extra servers needed.
Hope this helps!