the 24-70 is an incredible lens. and it is an "L" lens. it's a little long on the short end as your only lens however if you want to do real landscapes and cityscapes. the 24mm on a 1.6x crop camera like the dreb means the shortest effective focal length is about 38mm which is not very wide. you may also consider the 17-40 f4L as well. it just depends on what you shoot. the 24-70 is my main lens on the 20d and i haven't found a comparable lens as far as deep colors, contrast and sharpness go. on the downside, it's pricey and it's pretty damn big so it's not very discreet at all.