Yes, you can SSH into it, but you cannot install stuff inside this limited service console. First of all, I believe VMware has created some "checks" that keep standard Linux binaries from running in this environment. Something to do with how they've compiled the kernel, busybox, etc., but there are a few extra symbols required for executing binaries inside this environment. Furthermore, your space is pretty limited in here - ESXi is meant to create minimally sized management partitions, and I doubt if there's enough space to really install something useful.
Furthermore, while the console is there, as someone else already mentioned, it is UnSupported, which means that in a production environment (where you want VMware to support you if something goes wrong) you should be using this limited service console unless instructed to do so by VMware.
