OS X 10.4.4 fixed several MAJOR issues that solely existed with the newly (at the time) released Powerbook G4 17" 5,9.
10.4.3 (the version shipped with the Powerbook) had a serious issue with the Power Mangement system, Graphics Driver and Airport.
For power management, the powerbooks were constantly auto-shutting off believing that they had completely lost all power (making the date reset back to March 2001.
As far as the graphics driver, when anything really intensive (like one of the effects used to warp a window when opening or closing) the entire screen would flash with random data pulled from the offscreen buffer.
The Airport would completely loose the ability to connect to any wireless network and in turn max out the CPU until you disabled the card. The only fix at the time was to restart the OS.
This update was released within a week of the Powerbooks being out on the market (so was resolved somewhat quickly).
By the way, these were not isolated incidents. My organization purchased 24 of these to replace the former 450 MHz iBooks.
By the way, I would like to give a shout out to the general manager at the Lynnwood, WA Apple Store who allowed us to exchange the 12 that we had purchased a month before (5,8's with 5,9's), including a significant refund (due to the price drop). We were so happy with her handling of the "non-situation" that we went ahead and replaced the last of our systems.
Getting back to point, point updates absolutely fix "hardware-specific" problems.