It's still clearly in need of some fixes, and I wouldn't recommend that people who require the use of their Macs and apps for business reasons upgrade just yet (quick example: SnapZ Pro isn't fully functional in Tiger, CheckPoint VPN - which my business unfortunately uses - doesn't work, Photoshop Elements 3.0 - which I doubt any professionals use - doesn't work, etc.).
However, for casual users or those with dual-booting capabilities (ie.e, who can still boot into Panther), it's a blast to play with. Spotlight and other features are fantastic, absolutely great.
But pro users should wait or be sure they can boot into Panther.