First I have to say "What about Mercurial?" At the very least "hg" is easier to type than "bzr" ;) . It's also written in python, it's much, much faster than bzr when downloading/uploading stuff and is much more space efficient. http://www.selenic.com/mercurial/
About bzr... You can get the status/diff/... of everything starting with the current directory with something like "bzr status ." . I think a checkout is just a branch without the history (but then again I'm a bit confused with bzr's branches/checkouts/repositories...)
I'd suggest trying Mercurial too. It's somewhat more minimalistic than bazaar-ng but very easy to use and powerful. It deserves a try... and even a blog entry of its own ;). Hope this helps you find a nice DVCS that suits your needs.
It might be hard to find one that meets my needs, since if you'll remember I have no real needs ;)# Ian Bicking
In regards to "track changes in different checkouts" look into bzr missing bzr missing http://blah.com/other/branch ran from the root of your branch will spit out the revid logs for what differs.
Finally... for checkout vs branch, _my_ understanding is the same, checkout will be used for creating bound branches, eg think cvs co where you get just the working files instead of full history- history related operations will have to access the actual repository.# anonymous_coward