I think Apple has a problem with it developing such big OS updates (i.e. Jaguar and Panther, 10.4?) in such a short amount of time and then charging for them. It is simply too expensive for most people to upgrade every year (esepecially when you factor in iLife updates and other software). Sure, you don't need Panther, but if I had not upgraded, I would have been stuck with a verison of Safari that was buggy and could not load secure sites for me. This was fixed with Panther, and I can't see why it needs core Panther technologies for that.
If Safari, an independent app from the OS, is so closely reliant on core OS technologies, then Apple should consider providing at least a cheap upgrade path for users of the previous version. After all, if you already have Jaguar, you are paying the full price of Panther to upgrade, even though much of the product is the same.
Sure, there are comparisons with Windows and IE explorer. Ok, so I wouldn't expect any software updates for my Win 98 PC at home. But that OS is 6 years old. Jaguar was being sold for new until last October.
Sorry for the rant, but I feel that if there was a better upgrade path, the current Jaguar 10.2.8 runners would feel compelled to upgrade. As it is, Panther is better value for 10.1.5 users and excellent value for OS 9 users (presuming their computer can run it!).