Sure, using lightweight concrete will save you from slipping a disc while moving that shiny new cement-based chaise lounge into the study. It can also provide increased protection against fire. Mixed with an aggregate of shale, slate or clay rather than limestone, lightweight concrete offers an even lower heat transfer rate -- and therefore increased fire-resistance -- than the traditional version of the building material. While it can be designed to reach a similar strength as traditional concrete, some forms of the lightweight material may not be suited for structural purposes [sources: National Ready Mixed Concrete Association, Bilow].
A number of manufacturers also offer lightweight concrete finishers, which require more attention than the old-fashioned heavy stuff and take a bit longer to dry [source: National Ready Mixed Concrete Association].