To be honest. Tiger is not that great. However, it's an upgrade! It means that you will have to upgrade either now or later. Some people won't upgrade with tiger and rather wait for 10.5 . Others, who have extra cash don't mind upgrading.
dashboard, spotlight,safari RSS and automator are excellent tools but the tiger package is over priced.
I recommend that you wait till the time to upgrade becomes essential (software no longer supports 10.3 which is rare) or do the upgrade with 10.5 which I hope has more reasonable features compared to price.
I personally purchased tiger. I always use dashboard. I find it very helpful, but some times I regret what I spent on tiger.
You will get the best deal from Apple stores, they offer free training sessions and the sales people are friendly and will expose you to tiger's new features by domenstrating them in front of you.
In the end it's your decision.