Re: something like linum.el ought to be added

[Richard Stallman]

    >> Is it efficient enough?
    >
    > Many users have reported good success, and it works well for me too.
    > Please let me know if it doesn't work for you.

I'd like some people here that have slow machines to try it and
report whether it is fast enough to be usable for them.

    A large number of overlays is slowing down every operation in the
    buffer.  Having a set of 50 or so that is only adjusted upon redraw
    should be the fastest option for that reason.  If the overlay creation
    is time-critical, one might move keep some off-screen overlays in a
    separate list for reuse and detach them from the buffer temporarily.

Those sound like improvements.