In reply to FunkyNick:
Advantages of double ropes:
1. Less rope drag on routes which wander around rather than go straight up or down
2. Allow you to use gear placements over a wider area
3. Longer abseils are possible
4. If one rope is damaged, then you still have another one!
5. More versatile when setting up your belay.
Disadvantages of double ropes:
1. heavier
2. more expensive
You will always be climbing with a partner - often with double ropes, each climber buys one. You will only need to buy two if you will be climbing with people who don't own one...
Also, have a look at what people who have been climbing for a while are using - in general, most people doing trad routes use doubles. Those who use a single rope tend to be either sports climbers - sports routes tend to be straighter so rope drag is not so much of a problem and you don't need to use gear placements over a wide area. Or they may be people who have come from a climbing wall background, where a single rope makes much more sense.
Hope this helps you to make a good decision! You will then have all the fun of deciding WHICH rope to buy!
fun fun fun! My mate reckons that there isn't much between them so you may as well have a nice colour! (not my view!)
I've always just bought one half rope and climbed on doubles with my partners rope...
mich