It's sad and amazing how few people rely on tab completion, both in the PowerShell ISE and in the console window.
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When you tab complete, you'll never spell commands or parameter names wrong
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For many parameter values that are static lists, or easily-queried lists, tab completion (especially in v3 and later) can fill-in legal parameter values for you
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Tab completion makes long cmdlet names a lot easier to type, without the need for difficult-to-remember aliases.
Get into the habit of using tab completion all the time, and you're guaranteed to make fewer mistakes.