Diskless Machines In Your Environment

In your environment, have you ever used diskless machines (e.g. booted with BOOTP/DHCP/TFTP) for any reason? Where in your environment are you making use of them (e.g. what types of servers - web, application, database, DNS, etc...), and how has it turned out for you?

Has it actually yielded any of the promised benefits that the literature on them says, or was it a pain to set up and maintain?

Any interesting use cases on what you use them for and, as importantly, what are your criteria for determining whether a particular type of server should be diskless or not?

As this forum is filled with people with lots of experience running hosting businesses or their own web applications and therefore have managed thousands of machines between yourselves, I figured this is an appropriate and interesting question to ask. I'm hoping to get insights from here that I can't get from reading any old web article.