A welcome, functional module, sadly seriously lacking in documentation and extended features. The XS portion of the module seems flawless in my somewhat limited usel the perl API is just messy, with all sorts of exports going on, most of the listed in the POD without explanation. All error reporting is via an exported scalar.
For docs, see the spread.org website docs for the C interface, to which this is a pretty straight interface.
For extended features (daemonising, etc), try to compile Spread::Message.
In about six months of non-stop use, handling about 20,000 messages a day, the only real problem I've had with this module is its silly version number, which is in fact a string, and which all your usual MakeMaker-like $VERSION-detecting strings will ignore.