To make things easy for developers, the configuration API of Salta was copied from Guice (without the SPI). The concepts of modules, bindings, JIT bindings and scopes was taken over as well. Thus, if you know Guice, the learning curve is very gentle.
The only truly new concept added is the Creation Rule, used to construct injection point specific instances.
Classpath scanning is slow for big applications. Salta helps to avoid it by providing fully customizable creation of just in time (JIT) bindings.
Care has been taken to make sure the order in which the JIT bindings are constructed can not affect the outcome. Otherwise, different runs of your program would lead to different objects beeing injected.
To instantiate objects fast, Salta relies heavily on bytecode generation, resulting in a speedup between 10x and 30x over Guice.
Bytecode generation does not lead to slow startup speed. Salta is consistently slightly faster than Guice.
Salta has been designed from ground up to be flexible:
The wiki contains more information about extending and customizing Salta.