Re: Tiles should replace icons fully - everywhere.
Maybe most business users don't stare at their desktop to see 'important' information. The notification panel that has been around a fair while can update you with anything important, but most of the time people in work (at least the places I have worked) rarely see the desktop, they have their actual work open on the PC whether that be the Internet, e-mail, Word, or proper applications.
Even starting up the PC jumps straight to the corporate intranet and starts up e-mail in many places.
Windows introduced Gadgets a while back and I never found them that useful, Live tiles are almost the same in that context but less useful.
On a phone or possibly even a tablet a quick glance at the 'desktop' to see if there are any new notifications or updates works okay. On a PC, especially a business PC it doesn't. That is the issue with Microsoft especially with Windows 8, they never actually thought how a user actually uses a PC different to a phone and tablet, especially for business user who aren't obsessed with social updates.
In fact the OS really doesn't matter much to most business users (not including tech departments) at all. It's all about the software and applications that people have to run to do their job, they just want the OS to allow that as simple as possible and a simple menu with about 10 programs supports that quite well. Learning to use a radically new OS just to do the same work is definitely not a positive.
[Edit: I see after I posted that Tom 35 has the same opinion]