> I realise we're agreeing on the meat of the issue, so feel free to
> ignore the following: the essential difference between writing a load
> script and using Metacello is that if one of the packages I use - Bar
> - upgrades something that _it_ uses (Baz) (and about which I don't
> care), then without my doing anything more than saying "my package now
> uses Bar 2", everything still Just Works. It delegates the
> responsibility for building Bar to where it belongs, with the Bar
> developers.

This is exactly how SM handles it too, there is no difference here.
The "head" release of Baz would load the head release of Bar. By
selecting "install" on the head release, it merges the latest version
of Baz without having to care about it.

http://wiki.squeak.org/squeak/6182