I'm willing to be persuaded that Maven could be an improvement over raw Ant. But when I look at how Maven is put together it unsettles me. In trying to deal with that 2% I think they've overcomplicated things and forced themselves into making a lot of decisions in a short period of time which I wonder if they'll regret. I've seen this *so* many times and the results are rarely good.
Maybe XSLT isn't the answer - or maybe it's the whole answer or part of it - I don't know. But the "big bang" release of Maven leaves little room to rework design decisions without breaking things - it's the waterfall model all over again.
One final thought, which I came across this morning: Orgel's Rule which states "Evolution is cleverer than you are" (http://www.shirky.com/writings/evolve.html). Start with a worse-is-better solution and see where that takes you - if XP has one lesson to teach us it should be that one at least.