If you are going to evaluate, here are some random bits to pass along from my experience implementing build automation at 50 companies: (and no criticism implied whatsoever to other posters by my cynical tone)
- If you have a budget, you can often get far better tools - sorry, open source guys, but it's true. Consider if they are worth it.
Beware following software tool trends, but at least you'll be in a large club where you can easily get good and bad advice.
- Make sure the tool does what you need and beware the claim that something "can" do do something as opposed to "does" do something. That usually means it's extensible by some obscure means leading you down a path you don't want to be on. 3rd party plugins tend to be weak. Make sure the tool does what you need it to do pretty much out of the box/as downloaded or it is probably the wrong tool to use.
- Open source is big on innovation and features but poor in stability and support. Commercial tools the opposite. But not perl or other rare, successful projects like Apache, JBoss, Linux (which are not dev tools). Projects vary of course.
- If you are a really small place(<15 developers), probably stick with all open source tools.
- If you are a crack open source developer, then open source is great because you can fix the bugs you need fixed.