I like Ant but only if you spend the time to write your own Java plugins to encapsulate complex actions. It isn't hard but unfortunately most people try to write their logic in XML w/the ant-contrib stuff. I think this is a huge mistake.
I've heard good things about rake and the groovy tools (mentioned in another comment) but I've got no experience with them.
If you're trying to script together several steps in a life-cycle you might be better off using a process automation based build server like AnthillPro (Cruise, BuildForge and Electric-Commander are the others in this space).
Another place to ask this kind of question is the CITCON mailing list. CITCON is a conference on Continuous Integration and Testing and the associated mailing list has turned into a really great community around these kinds of topics.
(I'm an organizer for CITCON but a labor of love not a profit maker. It really does have a really helpful mailing list. If I was pimping something for money it would be The CI Guys. ;-) )
