I concur with Daysleeper, although there is more to Tiger than just the native 64bit processing on high end G5s. In general, all G3 and G4 Macs should run more efficiently and reliably under Tiger. I've been using Macs since System 6.0.2, and there has never been a more reliable system than Tiger.
Dashboard is more than a gimmick. Yes, it does rely somewhat on having a broadband connection, but once you have that, it does become a useful tool. There is the weather widget included with the system, but there are many more weather-related ones available from
Apple's website, amongst over 1000 widgets. There is an excellent Aviation Weather widget which will give METARs and TAFs, as well as radar rainfall ones and other forecasting weather widgets. Dashboard widgets are essentially time saving, helpful applications which make life easier. Instead of navigating to a currency conversion website, the Conversion widget will do the currency conversion for you.
Daedalus: if you're going to upgrade your Mac to Tiger, just make sure you meet the minimum memory and hard disk requirements. 256Mb is the minimum, but 512Mb will be much better.
AppleMacster