I'm Dan and I'm addicted to VDI. This answer can (and does) span several books, but let's give it a go:
VDI is definitely in vogue, for sure, but remember - the basis of it isn't really new technology. Citrix Winframe started life on Windows NT and Citrix has been offering access to centralised Windows apps and desktops ever since. The ICA protocol is even older than that! In my opinion, the drivers haven't really changed a huge amount in that time - but what's achievable has. So, why centralise:
- IT always remains in control of the software and data. Government and Financial institutions love this technology, because Dave in accounts can never leave his laptop containing the Year End Reports on the train, or whatever.
- Insanely easy image management. Ever completely updated Microsoft Office on several thousand machines before your first coffee? I have. Ever rolled it back before your second? (I haven't had to do that yet, but I could!)
- In addition to the above, with persistent images it's essentially impossible for someone to break their VDI image. Even with non-persistent, resetting it can be a matter of minutes.
- Thin Clients. This is really nothing to do with Kiosk Platforms in my opinion - a good VDI setup can give you nearly everything a PC can. The main difference here is being able to sit on any client in the organisation or have yours swapped out in a matter of minutes. Done properly, the fact it's a Thin Client can be essentially invisible to the user.
The list really does go on and on and every company will have their own justifications for it. The one thing I do believe, however, is that the main winners are the IT Department. Now, don't get me wrong - this can be good news for users in an organisation because they get things fixed and rolled out quicker, but with the exception of remote access I suspect most users would prefer their own machine (when it's working properly)
With regards to Cost - You're completely right. Anyone who attempts to use VDI as a cost saving measure is going to end up in a world of hurt. VDI done properly is expensive, there's no doubt about it - you need good people, good project management, good hardware and a good design. Done cheap, VDI will be nothing but a pain and your users will hate you. That said, VDI can be cheaper administratively in the medium to long term, so it can definitely be cost effective, but I never treat it as a money saving measure.
So, it that good? It can be - but doing it properly is complicated. I've had excellent feedback from users - especially those moving from old XP clients to a new Windows 7 VDI deployment, but I've also seen some absolutely horrendous engineering. The problem being that if you lose the buy-in from the users, it's borderline impossible to recover from - they'll simply see it as "rubbish". But, I am sincere in my belief that VDI can provide an excellent user experience. You're not going to be able to virtualise every workload (We're kind of where servers were 8+ years ago) but most office workers make excellent candidates. Interestingly, the last organisation I worked in even put their IT team on VDI (Save some emergency Fat Clients for obvious reasons)
As I say, this answer could go on for ever - but to answer your question. Is it a silver bullet? No, absolutely not - it won't fix everything and not everybody can work well on VDI. Is it an excellent option? Definitely.