On my iBook Tiger seems to have more bugs than Panther ever did. These include
1 - Safari regularly freezing and crashing.
2 - It is also beachballing sometimes for up to 30 seconds. This may well be (dialup) connection related, but I don't recall it being this bad on Panther.
3 - Finder will not allow me to move an item into any of my Movies, Music or Pictures folders by dropping it on folder in the sidebar.
4 - Finder in column view mode does not always accept using the left cursor key to go back to the folder last viewed. It never seems to remember the preview window setting either, especially when switching back from icon or list view.
5 - Finder maxing out CPU and hanging when attempting to preview an avi formatted movie file. I know there is no QuickTime codec available yet, but can't Finder just display a generic icon instead of giving up the ghost.
6 - Incorrect lengths of mp3 files in preview window too
7 - Dashboard weather widget crashing or simply not working. But given the RAM that widgets use and the noticible slowdown this creates I've stopped using them completely.
8 - iPhoto totally screwing up images after they are edited in any way. This is a major source of annoyance.
I really hope that some if not all of these bugs are dealt with in the 10.4.2 update. As has been said, Tiger feels very much like a public beta than a final release.