It's indeed nice that Mac allows us this flexibility, so we can pick and chose between the best of both worlds.
I have to disagree with you slightly, Mark. Mac doesn't allow that at all. Parallels isn't produced by Apple (it's produced and licensed by Parallels) and Windows' licence (provided by Microsoft) is what allows you to run it on a Mac, whereas OS X's licence (provided by Apple) is what doesn't allow you to run OS X on a PC.
Virtualisation tools exist on the PC that could quite easily run OS X if not for Apple prohibiting it in their licensing terms.
Even if we take BootCamp into consideration, it is still the less restrictive licensing of Windows that effectively allows the flexibility and not the Mac hardware or the Apple operating system.
As to Excel for Adults on a Mac? Well, here's a snapshot from December 2009:
http://arstechnica.com/microsoft/news/2010/01/windows-7-growing-faster-than-vista-overtakes-mac-os.arsAnd here's a snapshot from more recently (May 2011):
http://www.itsabhik.com/news/windows-7-joins-the-party.htmlIf anything, Windows is a tiny, tiny fraction more than it was in December 2009, but it's close enough to call it even. I'm sure that Microsoft could drop support for OS X and not miss the revenue (particularly given the frequently changing environment that is OS X and the costs associated with continued development), but they presumably have determined that it's profitable in some way.
Outside of the design world (photography, et al.), parts of education, and a few tiny fractions of the home market, OS X is only less trivial in numbers than Linux, a comment that will no doubt upset a lot of people on these forums, but it's a fact. Indeed, it's a very hard and significant fact that should easily answer every person who ever asks, "Why isn't Photoshop available for Linux" or "Why don't printer vendors make drivers for Linux" (they do, in some cases, but it's been a growing trend that doesn't encompass all of the vendors) and so on.
This isn't a reflection of which is better, friendlier, more stable, more fun, less this or more that or anything except market share, in which case the differences are actually an order of magnitude - when you're discussing percentages, that's pretty significant :-)
Personally, I hope that Apple does not abandon the personal computer/workstation/professional user market - competition is a wonderful thing and Apple has brought many excellent contributions to the market. So, even though I'm a Windows guy and not a Mac guy (but I use Macs at work alongside Windows every day), I'd see it as a huge negative to lose Apple/OS X from this segment of the market (just as I would see losing Linux as a downside, but less so).
At any rate, I would expect that printer vendors will provide driver updates in a pretty reasonable time after the release of Lion. I'd bet on current models receiving priority, then progressed in reverse by release date/model currency, as makes sense. Software such as Epson's LFP Remote Panel relied on Rosetta for the installer - not for the application itself. Once Lion is released, you might expect some official comment to be available from the 3 main vendors - relatively few comments are ever made regarding unreleased software or operating systems, particularly when the release is outside of the control of those vendors and/or covered under various agreements with Apple, Microsoft, etc., and Apple is infamous for not giving advanced notice of, well, much at all :-)