I am considering using Maven for a Java open source project I manage.
In the past, however, Maven has not always had the best reputation. What are your impressions of Maven, at this time?
For an open-source project, Maven has some advantages, especially for your contributors (eg mvn eclipse:eclipse).
If you do go with Maven, the one rule you must follow religiously is: don't fight the tool. Layout your project exactly how Maven recommends, follow all its conventions and best practices. Every little fight you get into with Maven is a day you won't be spending writing code for your project.
Also consider up front where you want to deploy your artifacts (are you going to host your own repository?).
And don't be afraid to go with something other than Maven (eg Ant). The success of your project will be the project itself, not its build tool (so long as you choose a best-of-breed build tool, which both Ant and Maven are).