Why do all deployment systems suck?

At HubSpot, we have a pretty wide array of different things being used for the webapps running behind the scenes. This isn't surprising. There'a also some home-grown scripts (in python, as that's the scripting language of choice... something I'm not complaining about) to take care of deploying the various webapps. It works, but I really want to get it doing a bit more so that it's more useful and also get the different scripts doing a bit more sharing of code so that we can improve one place and get the benefits for everything.

Given that this seemed like a pretty typical problem, I figured I'd take a look and see what open source projects exist out there to see if any of them were suitable or could be at least close to a good fit for what we need and want. Unfortunately, I was kind of disappointed...

• Capistrano seems to be the big player in this arena. It was originally written for Rails and still very very strongly shows that heritage. This isn't necessarily bad, but it makes it a lot harder to get to work if you're not doing something that's rails-like. There are some people who have gotten some things working with Java app deployments for tomcat, but they all feel a bit hacky. The other downside for me/us is that Capistrano is very much Ruby-based, both in how its own deployment language looks as well as some of the "how it depends on things working" aspects. Also, the fact that it's written in Ruby and thus a little bit more difficult for us to hack on if/when we run into problems is a point against. So it's probably a non-starter for now, or at least a pretty difficult sell
• Fabric is written in python and seems to be following in the footsteps of Capistrano. Right now, it's far far simpler. This is in some ways good but some of the pieces that we'd want (eg, scm integration) aren't there and so I'd have to write them. And I'm not sure if the Fabric devs are really interested in expanding in that way; haven't sent email yet, but planning to tomorrow to feel it out.
• Config Management + Binary deployment is the approach taken in Fedora Infrastructure for app deployment and it seems to be working pretty well there. It might be something to get to eventually, but that's going to be a longer term thing and I'm not actually convinced that it's really the best approach. For Fedora it grew out of only a couple of things which could be considered "webapps" and a lot of system config that has turned much later into more webapps. It also pre-supposes a bit more homogenous of an environment than we use at HubSpot from the work I did there
• Func is something that a few people have been working on that I keep wanting to find a use for but it seems a little less well suited to doing a lot of java app building/deployment given that it's more https/xml-rpc based than shell based.
• Roll your own is what we're doing now and what it seems like is pretty common. I don't necessarily like this, but it's certainly the path of least resistance

So, what am I missing? Is there some great tool out there that I haven't come found that you're using for Java (and more) webapp deployments? Bonus points if its python-based and pretty extensible.