I also wouldn't trust Tiger security on an external network.
And I preferred spotlight in 10.4. In fact, 10.4 was all around a much better OS than 10.5, which was the first update to Mac OS X that felt like a step backwards.
Of course, I'll be updating to 10.6 as soon as I can get my hands on it. If nothing else, the promise of a 10.5 that doesn't suck is worth it. To be fair, 10.5 is much better now then when it shipped. When it shipped, it was terrible.
(a) intentionally, knowingly fixed
(b) disclosed.
I think you've fallen for the marketing trap where a list of features has to be present for it to be worth something. Not many lists include code and platform optimizations because it doesn't market well. I've used OS X since 10.1 and each update has gotten remarkably better. Things have mellowed out in 10.5 but the OS feels fully baked.
In the end I don't think there really is anything they can do to make me pay more money for the OS. I already bought iWork 08, I bought SuperDuper! for backup, and everything else I use is either open source or comes included with the machine. If Apple wants me to upgrade, then they need to discontinue security updates for 10.4 or some widget I badly need needs to be 10.5+. And honestly, it's not me that Apple has to contend with, it's my wife and her iron grip over the budget ;)
I'm hoping that a scorched-earth fresh install of 10.6 will either eliminate the amazing flakyness or alternatively point me to a hardware problem.
It could be if you were required by some regulation to use a UNIX certified OS. IIRC, there were little feature changes that warranted the certification.
As for myself, I have an older iMac that won't run SL, a netbook that runs Linux and I am perfectly happy with both.