Earlier today I completed upgrading my MacMini to Leopard and it somewhat surprisingly feels faster than when it was running on Tiger. Apple’s Ironic Bluish Screen of Death was the only serious issue that I ran into, but by repeatedly trying “Option C” in their recommendations I was able to get back up and running.
Of the 300 New Features, the one I was most interested in was Dashcode the Apple Dashboard Widget Development Environment. I’ve been banging my head against the wall trying to squeeze the last few bugs out a widget I’ve been developing and Dashcode has been a godsend.

Prior to this, you needed to alternately load your widget up in Safari to develop it’s outward interface, then load, remove and reload the widget endlessly off the Dashboard as you got into the widget.() specific class features. Both of these testing strategies can now be tossed out as everything just runs inside of the Dashcode environment. One last very slick feature is that Dashcode really eases pulling together the disparate parts needed to get a fully fuctional widget going: plists, icons, images, etc. nothing you couldn’t do by hand, but much easier and quicker with Dashcode.