I've just done the upgrade of Tiger to 10.4.2 (thanks Tao of Mac). It went smoothly. Exactly two weeks since I last had to restart the MacTop, not bad when you think I've only had it for 3 weeks!
No sign in the release notes of anything new vis-a-vis BlueTooth so probably my Motorola HS820 still won't work, I'll try it out later.
Oh and I've disabled Dashboard. I never use it.
Disable Dashboard Eminently simple. defaults write com.apple.dashboard mcx-disabled -boolean YES Either of the following to turn it back on again. defaults delete com.apple.dashboard mcx-disabledAfter logging out and back in again you won't notice any change in the Dock Icon for Dashboard but it's definitely not running.
defaults write com.apple.dashboard mcx-disabled -boolean NO [From RixStep]