Chris,
As with the others, I too have had no problems. But if you are especially apprehensive, you may care to DL the upgrade, boot in to Safe Boot mode and then install the upgrade from there. That will essentially preclude all nonessential Apple functions as well as third party apps, scripts, haxies, plugins, etc. from loading; and thus their interfering with the installation process.
Only takes a minute, and can't (well, shouldn't) hurt.
Immediately after the install, I suggest you Repair Permissions (and run DiskWarrior if you have it).
After a few days of problem free operation, you may care to again check for (any) updaters that are predicated on 10.4.11.
And oh yeah, before you begin the upgrade, you have at least 1 verified backup???
HTH