Ah yes I remember this! I was always bad at typing out the numbers though. We support range selection as well, but it does require a keypress for each (which is less than ideal if you have a ton of entries).
Maybe we'll integrate some kind of line-number-selection-mode one day!
https://gist.github.com/aristus/2304335
One of the most useful features is range selection syntax, eg, run git rm on items 4-16.