So for example, I uses VBscript to script out my tasks in Windows, and more recently PowerShell.

From a Linux Admin's point of view, what scripting would he/she need to know? Would being proficient in Bash be sufficient or should you supplement that with something else? (if so, what is that something?)

PowerShell looked very cool; not easy to learn but nice; how were your experiences? I only dabbled and then switched to Linux.

Getting back on topic, so much of Linux (strictly "Linux-based distro" because Linux is "only" the kernel) is written in shell script that a sysadmin without shell script is like a bird without wings and bash is pretty much essential, or at least the POSIX-ish subset of it.

As ever, it's "horses for courses" and bash is not good for everything but, being a command shell its shortcomings can mostly be made up for by using other tools within bash such as awk, bc, sed and tr.

PERL and python are popular too but I've got by without them for a while now.

That "something" could be ANYTHING. For shells, there's bash, csh, ksh, and tcsh. All a bit different from each other. There's perl, ruby, python, and tcl also.

For Linux, figure out what you want to DO first, then use the best tool to do it. There are no hard and fast answers.

True, but since bash is so very common in Linux environments, I'd say it's a good starting point. Some places tend to use (t)csh instead, but I don't think I've seen more than one that didn't have bash as an option. Like said, with the small knives and forks like awk there's not much you cannot do with it. When that happens, many grab either perl or python, but at that point you're pretty much free to choose whatever you either already know or are eager to learn (i.e. there are no "bad" options as such).