It doesn't make much sense to compare it to any of those languages, it doesn't try to solve the same problems. Io is a minimalist's scripting language in the same space as Python, Ruby and Perl. It's also very suitable for embedding, like Lua. It aims for a performance profile similar to Python's, which sets it apart from some high-performing high-level languages like Lua, Javascript, Java, Scala and Go.
Its incremental GC makes it somewhat suitable for game scripting. It uses a single OS thread with coroutines, like Lua, although it supports multiple VMs in the same process, so asynchronous message passing between two VMs on separate threads might be easy enough to hack together.
It's good for people who like the minimalism and dynamic nature of the language and what it lets them accomplish, so long as their task isn't CPU-bound and doesn't require a rich library ecosystem.
Its incremental GC makes it somewhat suitable for game scripting. It uses a single OS thread with coroutines, like Lua, although it supports multiple VMs in the same process, so asynchronous message passing between two VMs on separate threads might be easy enough to hack together.
It's good for people who like the minimalism and dynamic nature of the language and what it lets them accomplish, so long as their task isn't CPU-bound and doesn't require a rich library ecosystem.