Hate to respond to myself but I forgot to add:
I don't necessarily agree that every company should just drop their hardware and get thin clients...
I think the right type of company, with the right amount of users will save money long term by properly building their own private cloud and offering virtual desktops. Even if that private cloud of theirs is being managed by a 3rd party.
100+ users I would say go create your own private cloud.
You are a collection agency / call center? Even better reason for this... I can't tell you how many times I was forced to move computers around or re-image a huge group of physical PCs because some client decided to cut their staffing levels in half.
Managing a cluster of enterprise level hardware will always be easier than managing a hodgepodge of general purpose workstations that were all bought at different times... (assume your "replacing 1/5 your towers every year" or sooner based on customer requirements).