William,
As someone who has updated a rather large number of Macs to 10.4.8, I can tell you without any doubt at all that there is nothing wrong with the update. What tends to happen in these situations is that updating a system brings to light issues that pre-existed and which should have been fixed before updating took place. There are instances, for example, where as a result of utilities used or add-ons installed, the software update process may mis-identify the particular model of Mac you are using or the components it contains, and download the wrong, or incomplete, update. The easy fix is to download the full 10.4.8 'Combo' update from the apple/support/downlaods page and install that. This resolves most updating issues because the combo update contains all the components and recourses for all systems.
By the way, what you read here is primarily going to be complaints about faulty systems or software, so while it's informative to look at what other people are posting, it isn't indicative of anything much other than that some users are having some problems. It's a bit like a hospital waiting room, where the people are typically going to be sick other wise they wouldn't be there - but you can't, of course, infer from their presence that the entire city is sick!
MacOS 10.4.8 doesn't slow systems down at all. Bad cache files, poorly maintained systems, conflicting fonts, out of date prebinding, erroneous permissions, damaged properly lists, etc etc, are all capable of causing system performance issues and all need to be examined and resolved. As a Linux user, no doubt you are familiar with these concepts.
As to Apple support - your perception may vary, but they still score consistently high on the consumer satisfaction surveys of such people as JD Power and PC Magazine. There is always room for improvement of course and Apple is far from perfect, but one thing that we do see happening a lot is that as new users join the throng of Mac owners, they tend to bring their expectations of need to run maintenance and utility software with them from other platforms. What is often needed in Windows, for example, to keep a system running well is rarely needed in MacOS - and can actually create issues rather than resolve them.
Oh, and:
I have done nothing to my system.
Setup 7/24/2006, used it for web, creating doc's and email.
Got no help from Apple because it's been 90 days.
10/28/2006 or 10/29/2006 looks like they timed
the update to cause systems to crash so they
could charge for support in fixing it.
Is just plain childish. Firstly, that supposes everyone bought their systems at the same time as you did, which I'd imagine you can see is a bit unlikely. Secondly, it flies in the face of the majority of users who report no issues. Thirdly, Apple wouldn't survive long if they had that sort of business practice. Fourthly, it abdicates all responsibility you have for your own system.