The 24-105mm f/4L is my lens of choice as a walking around lens. Not quite as much reach as the 135mm (I just got that lens, awesome!), but still has plenty of reach. The one single spot where it is not as great is it's f/4, so it's a bit slow, and you don't really get a lot of bokeh, although it's decent if you're zoomed in and your subject is pretty close. Also, at 24mm it has a some distortion, although Lightroom does a good job correcting for that. Sometimes I actually kinda like it, it all depends on what the shot is.