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Full user review
"The Best [Now Only] Freeware Subtitle Editor I've Used"
It's free (although I donated a bit), portable, has a clean interface, has many useful tools, has an Undo history, and you can add your own words to the dictionary and-or OCR fix list.
It can't get me a beer from the fridge ;-) .
The other reviewers already wrote it, so I'll simply type: highly recommended.