Josh Smith IS Atlanta's best player, so he better be starting still. I actually really like the lineup of:
1 - Bibby
2 - J Johnson
3 - Josh Smith
4 - Horford
5 - Zaza
In theory. If they had picked up a better C (like Shaq) I would of really liked that lineup, but as is it still is viable. You give up some shooting ability but that team can crash the boards strong and be really tough inside.
This team proved they can't handle Dwight Howard at C at all, so it was obvious for them to legitamately contend they will need Horford to be a PF, not a C. With that much size they can hopefully body Dwight and Horford and Josh Smith are two great guys to be bringing in help defense against Howard.
Josh Smith at SF is not perfect, but although he might give up some quickness he is a great athlete and certainly will bruise other SF's. He will be a matchup NIGHTMARE in transition with that lineup.
Also, Marvin Williams is then a bench guy and is that much better in that role than he is as a starter.
I think they do keep using their regular lineup against most of the league but against Magic and other big teams inside (probably us included) they will try this sort of lineup. I think it has upside for sure.