One of the main reasons for using any build tool is to get reproducible builds. That is to say that the build you do today can be exactly replicated in a years time. Maven, in my experience, fails horribly at the test of creating reproducible builds.
The problems stem from being a large and complex beast with many moving parts. Each part has its own release cycle, and the versions often conflict with one another and break your build. Trying to debug such a thing is very complex.
I use Maven for open source work because it produces a reasonable website relatively quickly. That is something rarely of interest to non open source developers. Even with this task I have frequently spent long periods of time trying to work out why things aren't working as expected. For the open source work I usually use ant to actually produce the build (jar) as that is reliable.
One final point. If you are writing an open source project you may have to use Maven in some way. If your project is popular then you'll need to get it in the central Maven repository, and that is much more tricky if you don't use Maven.
