seems like bad business to use macs, simply because if they break you have to send them in to apple rather than have the local IT guy fix em. also, cost.
You make it sound like IT departments spend a lot of time dealing with hardware issues. The truth is, we don't. Most corporate PCs are not custom-built rigs that use standardized parts. In fact, most corporate PCs are highly proprietary, with non-standard power supplies, system boards and form factors - very much along the same vein as what Apple sells to consumers.
If one of my Lenovo desktops has a hardware issue, I have to go back to Lenovo, who will dispatch a tech to repair the machine (much like Apple would through the same outsource firms that companies like Lenovo, Dell and HP use). In fact, one of those techs who was on-site to swap the system board in a Dell Latitude, showed up with a Mac that he carried his service manuals on. Come to find out, he was also certified to repair Macs for his company.
Sure, there are systems we have that are out of warranty that I'll need to swap the occasional mechanical part out of, but those are few and far between - and usually it's things like fans, hard drives and optical drives, which are pretty simple to swap.
With that said, I agree that Apple has a long way to go until it becomes a viable alternative on the desktop in the enterprise. I wouldn't even know where to start if I had to manage Macs in our Microsoft-centric environment. Today, I manage thousands of PCs, using GPOs, SCCM, McAfee EPO and many other tools that just don't have Mac-friendly alternatives. Heck, I've read quite a few posts here and elsewhere, where IT departments have quite a bit of trouble getting Macs to play ball with AD.
iPads, on the other hand, have seemed to pique my company's interest. From what I understand, we are already testing their application in a number of different settings. Hopefully one of those will eventually fall into my lap.
