I'll try to stay in the Microsoft camp of technologies to keep it simpler. One of the first questions you should ask is hinted at by Jim B, but let’s assume you’re talking "thin clients" which is what a diskless node is:
Can you use presentation virtualization or desktop virtualization?
In more words: Can you get away with RDS (Remote Desktop Services) aka terminal services/Citrix or do you need the more costly VDI (Virtual Desktops)?
Med-V is out as it’s for managing apps on client hard drives and you’re on thin clients, so to me it's between RDS and VDI.
RDS is the good old terminal server now called a Remote Desktop Services Session Host. You install client apps on the server and users use Remote Desktop (RDP) to connect to a single server (or pool of servers) that runs multiple user logon sessions at the same time. These users are using a Windows Server 2008 R2 desktop, and if an admin looked at task manager they would see all the users .exe's running on one server. There are extra features that makes this user friendly through a web browser, load balanced/FT, and Remote Desktop Gateway which runs it all over SSL port 443 to make it Internet firewall friendly.
If your app has special requirements, and you have users who need their own Client OS to themselves, with their own C: drive, RAM, etc. that's where you can optionally deploy VDI on top of RDS. CAD may be a good example of this. So users are still sitting at thin clients, but when they logon to the remote session, they are actually using one of many Windows 7 client virtual machines running separately on one or more Hyper-V servers. They could still be all sharing the same physical server hardware, but now they have their own "world" to play in. Usually this is only deployed when a Session Host (terminal server) won't fit the bill.
Maybe if you describe the usage some more of the application and users we could help you narrow down the field of choices. RDS is great and rather easy to manage (compared to VDI and other options) if you can get the app to perform well running many times concurrently on a single server through multiple logins.
Citrix is usually only need to run on top of RDS when you go big to thousands of users, but even then the newest Windows Server 2008 R2 RDS can get you there.