Excel on Mac works fine, and we do some fairly sophisticated numerical modelling work.
In terms of Office, the bigger problem has been legacy Access databases. We solve this by setting up some VMs with RDP access for the Mac users. But there's also a couple Mac utilities that let you export Access tables to CSV which can then be loaded up into something sane.
A surprising number of people also use Project, Visio and OneNote and there's not really a good portable solution for those cases. I've been pushing people to use yED for portable charting (instead of Visio), OneNote is now available for Office 365, and people are finding Excel a good enough Gantt chart tool for many purposes.
Office on Mac is quite good compared to Windows, just not all of the products people expect to use are available.
The bigger picture thing is that this is going to happen and enterprises need to figure it out. Non-cross-platform applications and processes need to be abandoned. This also happens in reverse with remote Linux servers being easier to work with on Macs than via Windows (putty and winSCP sort most of the issues out, but they aren't perfect).
In my experience people really don't care about the desktop experience too much, IMHO Windows is better than OS X for most of that anyways, but they care about "getting shit done" and that means apps, and these days web-based apps. The OS just isn't that big of a factor so long as the things people need to GSD is available. They're choosing hardware and form-factor over OS and they pick the one they think will work best for them.
Well until a few weeks ago you where limited to 65k rows in mac excel.
Having struggled with OSX an apples obvious abandoning of any professional us other than a one man band designer - I hate apple hardware with a vengeance.
