Yes mainly slugs. However it depends what you plan to plant in the spring, say it is onions, which are less interesting to slugs or summer beans which go in later when its usually drier, then it can be ok. Also large plants such as squash don’t mind lumps.
Also cold winters with frost help the breakdown more than wet, warm winters such as we had here last year, so in your climate its worth a try. Keep us posted with how it works, maybe take a photo after spreading, then same bed in the spring.