Unblockus is a VPN service. It's not a traditional VPN service as it only works with sites and services that they support, such as Netflix. Also, you get your full ISP download speed with Unblockus as it just works by putting their supplied DNS into your equipment or router. If you subscribe to their service, you can choose the Netflix region you want to access via a drop down menu on their web site.
Netflix Super HD is only supposed to be available in the Netflix region that you reside in and if your ISP uses the Netflix CDN. The people at Unblockus seem to have found a way to give you Super HD irrespective of which country you are in and which Netflix region you are accessing.