Ubuntu is probably the best choice. I would go with the alpha of 10.10 as it will be released in October. It might be a little buggy but runs good on my computer.

Make sure to partition it with two partitions. One for root ("/") and one for ("/home"). Where root is not bigger than 10 Gb and /home as big as possible. The swap partition should be 2-4Gb depending on how much ram you have.

And install Avant-window-navigator or Docky. Also the Awoken theme is nice. It can be found on www.gnome-look.org. For torrents use Deluge and IM the Emesene. Wine could be good if you fancy Spotify.

Here is a really good blog: http://www.omgubuntu.co.uk/