It's sad and amazing how few people rely on tab completion, both in the PowerShell ISE and in the console window.
When you tab complete, you'll never spell commands or parameter names wrong
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
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.