[PeterisP]

For starters, if you'd want to eyeball a particular location in e.g. a 100mb data file that's not plain text but common text-ish formats such as xml or json, then you'd want prettyprint/reindent and syntax highlight; and using search/replace regex interactively gives much better immediate feedback about results (i.e. if this is what you wanted) than doing the same with grep/sed.