Hi, great questions.
Chef and puppet have a lot to offer. In particular, there are things that chef and puppet can do that babushka can't, like orchestrating ecosystems of multiple machines, and provisioning new hardware automatically.
Deployment is a problem that I'm very interested in, being a web developer and maintaining my own production machines, and I think babushka has a lot to offer in that area. However, I don't think of babushka as a deployment tool. I think of it as a "remember what I researched or learned the first time" tool, and part of that is deployment.
In building it, I'm aiming to build the most concise, powerful DSL I can for automating chores, and at focusing it as hard as I can towards the "no job too small" end of the scale.
My other main motivation is making babushka immediately useful and approachable, both as a user and a contributor—i.e. I want you to be running deps and seeing results within 2 minutes of discovering the app. And I want you to be able to write your own deps as easily and quickly as possible, push them to github with a single command, and have anyone else run or incorporate them into their own trees of deps equally easily. Most of that is already possible today using automatic dep sources, and the remainder I'm working on. :)
For example, Josh Bassett has been building a template for installing vim plugins: http://github.com/nullobject/babushka-deps/blob/master/vim_p... - which means you can automate the installation of your own plugins by writing a babushka dep like Josh's:
vim_plugin "vim-cucumber" do
source "git://github.com/tpope/vim-cucumber.git"
end
You can run that dep with a single command, even if you've never used Josh's dep source before:
babushka nullobject/vim-cucumber
And so on, to configure anything and everything you like. It's already doing this job, which I'm really excited about.
http://twitter.com/harvinius/status/13116470017Similar things are already working well for textmate bundles, OS X app bundles and installer packages, git repos, and so on. The idea is that babushka is purely the engine (plus enough deps for it to install itself), and it should be as fast and pleasant as possible to not only write deps like the vim-cucumber one above, but to create new templates and make new tasks I've never thought of. You can extend the DSL using the DSL. :)
So — I have a lot of time for tools like chef, and probably have a lot to learn from them too. I'm building babushka to be complementary to those tools. For example, part of larger deployments is doing specific, more focused jobs at certain points, which is something that babushka is just right for.