I have always used ANT to create build scripts, and by and large it has served me well. ANT is simple, and it has a wide variety of tasks, which take care of almost all build requirements.
Sometime back when I came across a new build tool called GANT, I was curious as to what it would offer that ANT did not. GANT is really Groovy + ANT. For those of you who are not familiar with Groovy, it is a dynamic language which compiles to bytecode and interoperates very well with Java. So GANT uses Groovy as the language to create build scripts. However all ANT tasks have been made available through Groovy's ANTBuilder. So GANT can use ANT under the hoods, but it is not limited to ANT.
If we need to write custom stuff for a build script, we can either create our own custom ANT task, or alternatively we can write a Groovy function or class. This along with being able to easily add consitional logic in build scripts is a very useful feature. Also since we use Groovy for creating the build scripts, we move away from the cumbersome XML syntax which ANT requires. All this in my opinion is a big advantage for developers.
However, there are a few drawbacks of using GANT. First of all, you will have to spend some time getting familiar with GANT and learning Groovy. Granted that they both have a pretty small learning curve for Java developers, but it's still time that must be spent. Also tooling support for GANT is not as good as it is for ANT. That's at least true for Eclipse. I am not aware of the state of GANT support on NetBeans and IntelliJ (Please share your thoughts in the comments if you have experience using GANT with either of these).
Even though I said that GANT uses Groovy to create the build scripts, what it really uses is a DSL (Domain Specific Language) made on top of Groovy. But within a GANT script we can use Groovy syntax freely. Again there may be some restrictions, but I am not yet aware of them.
There is the sample GANT script shown on GANT's website.
Here is how you might actually compile your programs in GANT
And see this page for an example of using the javac task in ANT.
Give GANT a try, you might actually start liking it over ANT.