When running a build for the first time it takes a long time to run bzr branch, its better to use --lightweight option.
I think you mean 'bzr CHECKOUT --lightweigth' ?
It is a good idea to minimize time and space during checkout, BUT, because of https://bugs.launchpad.net/bzr/+bug/264863, 'bzr missing' as well as 'bzr revision-info' won't have the good behavior : it will always return 'no missing' or the revision-info from the checkouted branch, and Hudson won't be able to compare current checkout revision with distant revision...
We have this in recent versions (it's an option).
Although in the future we may go to using stacked repositories instead, due to the performance issues associated with lightweight checkouts.