In reply to Gaston Rubberpants:
Firstly regarding the OP: The OP does not mention UK Trad. It states "multi pitch rock climbs" - no mention of UK trad.
I just don't agree, but each to their own. It does depend on where and what you are climbing. However, I used to climb on 50's and switched to 60's after being short of rope on a few occasions IN THE UK, especially in Scotland.
In the Alps: 60m are pretty standard now (just read the recommends in the modern guide books). In fact even buying a 50m is difficult in Chamonix these days.
Sport climbing: again 60m are pretty standard. A 50m rope is way too short for Ceuse or Kalymnos and many of the crags in Spain.
Ropes are so much lighter and thinner than they used to be. 60m of 8mm in no heavier than 50m of 9mm was 10 years ago. The flexibility that 60m ropes provide far outweighs the extra length you need to handle.
I just think climbing on 50m ropes is, well a bit old fashioned.
p.s.regarding point 4 (abseils): If you abseil with due care (i.e. use a backup prussic and know the ends of the rope) then using 60m ropes is actually safer. It means LESS time on the descent, and MORE options for finding good belays.
Cheers