Vir Linden has posted in the SL Forum BoM releasing Soon.
So, BoM will release August 26, Monday.
There is an RC level viewer for BoM here, which you can use now. Presumably, that RC Viewer will promote to the main default SL Viewer.
There mostly aren’t any BoM products to play with. But, you can jump to the Knowledgebase article on Bakes On Mesh and learn how to use BoM. There is also a step-by-step for making BoM stuff. For users, the use of BoM will be almost identical to how we use the classic avatar and system clothes.
I know Slink is ready to release their BoM compatible Slink bodies. We should see those quickly. Presumably, other major designers have BoM products waiting in the wings. So I expect BoM to quickly be adopted by a significant number of SL residents.
The hope is this feature will reduce ACI and improve SL performance. BoM should affect bodies, clothes, feet, heads, and hands. But, it will NOT affect existing mesh bodies and clothes. Those will all continue to work as they do today. Only new BoM capable stuff will use the new feature.