Just wrote this up on ITtoolbox.
Read the rest there.
Really , there is too much happening out there and way too fast. This industry is evolving every few weeks. I saw a couple of authors struggling to keep up the pace with all the advancements.
For instance, lets take VMware here. They first brought out ESX 3.0, a couple of writes/authors or experienced folks in the industry got excited and started writing a book on it. A lot of expertise was put into those books. Loads of scripts, loads of perl stuff and massively cool Linux commands. I've personally never seen a windows admin do a dd so it was really cool to see the guys go crazy with all those commands.
Developers start writing utilities like ESX update utility and loads of other little utility. Vmware goes ahead and releases its 3.5. Oops...plans change as authors have to struggle to keep up with the pace of all the changes that come in and get going with all the new (primarily) GUI utilities such as Update manager etc.
Then boom!!! Here you have the firmwarish version of ESX 3i and suddenly you don't need to get into your Linux consoles and all those custom scripts can go home as that thin, flimsy layer of near-embedded hypervisor is a simple keystroke up/down and all those F1, F2, F11 keys.