I got it because I get it for free from work ... but I would never pay for it. It might be better, but its not worth the $100 they want for it ... or maybe I am too dumb to tell ...
There are a number of Mac fan sites that discuss this in great detail. I upgraded when I bought my new MacBook. Based on my experiences, I wouldn't rush and buy the upgrade to Leopard. Tiger is still a pretty nice operating system.
I would wait a few months as they iron out all the kinks, unless you really need the new features. None of the things I've seen are really so good that I'd want to upgrade ASAP.