In reply to James1987:
I've been using a 50m Mammut Galaxy for the last year or so for a mixture of indoors and (straight-ish) outdoor trad routes and sport climbing. I've been more than happy with it for both.
With the indoor season kicking off I've just (last week) treated myself to a new gym rope. 50m is a bit long for indoors and I don't want to trash my decent dry treated rope indoors too much with repeated falls. Having some stretch left in your rope for outdoors is a good thing - softer catches (bolts outdoors are further apart than indoors) and less chance of ripping your gear if you move onto trad climbing.
Having shopped around a bit (and used a bit of discount) I managed to get a Mammut Vertex 30m rope for indoor use for a steal at £44 (rrp £55). if you're going to hammer a rope indoors, hammer a short, cheaper one (that's still decent quality!).
Mike.