Apple's US market share has in fact increased, climbing over the 5% barrier recently. Back when Apple started "5 down, 95 to go" they actually had about 4.7%. A number of analysts have been coming out with fairly optimistic forecasts for Apple's market share, largely because of the new iMac. If Apple can scale up production and ship about 1.5 million iMacs Apple will probably be up to a 6% market share. I've seen a lot of estimates that by Q4 Apple will in fact be over 6%.
There has even been (imo) surprising optimism from Wall Street that Apple could double its worldwide market share in a little over a years time. That would see Apple around 7% worldwide, and probably 7% in the US too.
It's going to be slow, but there seems to be a continental shift going on in the computer industry moving away from Microsoft, and toward Apple on the desktop. I wouldn't be surprised at all (and actually expect it) if Apple was comfortably over 10% market share (US and worldwide) in 5 years.
A recent <a href="http://www.computerworld.com/storyba/0,4125,NAV47_STO69691,00.html">interview</a> with the creator of Java, James Gosling, has an interesting little quote in it for example. "And from a personal point of view, I personally actually read the [Windows] XP license and decided I couldn't sign it. So I've been shifting over to Mac." If anyone can remember the industries opinion of the Mac and Apple back in 96, this is amazing. Mac/Apple bashing has almost disappeared and at the worst you get the admission "Yeah, Apple makes some cool stuff, just not for me." Attitude change is step 1, extracting the money from the wallet is step 2
We're at the beginning of step 2.
Cheers,
Dak