My 2¢...
I 100% agree with the sentiment that Apple should not try to have a meteoric growth rate. From what I've seen over the years, a company can grow to any size it wants and be stable, but if it does it too fast (or, frankly, if it does it for the wrong reasons) it becomes unwieldly and unstable, and eventually will die. I know people here will laugh when I say this, but I fully expect to see this phenominon happen to both Wal-Mart and Home Depot, just like it's happened to countless other companies who got too big too quickly.
I firmly believe that marketshare is significant in that it is a make or break for software and peripheral development. It is also significant in that it contributes to overall "mindshare". Now, you can accept or reject "mindshare" if you like, but it absolutely has an effect because people believe it is important.
Furthermore, I have issues with the comments about marketshare increase alone as a primary contributor to getting Macs back into schools. The reason I have a problem with that is that school boards and school superintendants are typically in the back pocket of the IT staffs of the district, and so many of those staffs out there are all MS-heads. Until you can replace those folks (not convert, not convince, but replace) you're hardly likely to see much penetration into the educational market.
And with both businesses and schools, it's incredibly ironic that they cling -- positively cling -- to Microsoft and all things Microsoft and only things Microsoft, even despite the tide of spyware, malware, viruses and incessant security hole exploitation. I mean, they'll bitch and moan about all the holes they had to patch and all the viruses they had to contend with and all the maintenance issues which fill up their day, but mention "Macintosh" just once and they'll immediately jump on the bandwagon of "Anything not made by Microsoft sucks. Oh, and Macs doubly suck, and nobody uses them, and there isn't any software for them, and they just crash all the time." Yadda yadda yadda. Geez, if I had a nickle for everytime I heard that crap come out of the mouth of an allegedly-savvy IT guy...
Anyhow, one factor of significant import is Linux's market share, which is now either equal to or slightly in excess of Apple's. It's a good thing, on the one hand, because it means that competition is alive and well in the OS marketplace. But it also should serve as a wake-up call to Apple. They should know full-well what this means, since they're (at least to a degree) in bed with the Open Source crowd.