In reply to samnbuk:
You may wish to consider whether you will get a second half rope at some point in the future. If so, then I would pair your new half rope with your future desire. Personally I am a fan of my 60m ropes because a) it's supposed to be better for winter where belays are far apart (but haven't really had a chance to play with that), b) the extra 10m has come in handy a lot for very long pitches (e.g. anything on Tryfan Bach) or long abseils (e.g. the allegedly 60m one off the Mot) and c) you never have to worry about having some spare rope at the belay if you want to use a lot in the belay or indeed go wandering 5-10m off in search of better gear at the top.
Others disagree - particularly those that only climb tiny sub-20m routes :P
Final consideration - if I had a single and a half, but was on a route of less than half the length of the half rope, I would consider tying into the middle of the half rope and using that instead of both ropes. You will get up quite a lot of stuff if you have a 60m half so can do 30m pitches...
I don't know what is standard for trad in Europe, so a lot of this advice may be irrelevant...
Using a single and a half works OK but can be a lot of rope and faff. Using a 50m and a 60m should be fine - as long as you tie knots in the end for abseiling and sport lowering (but you are doing that anyway, right?) :P
Post edited at 16:55