for hobby folks, i have a strategy of buying: because if we buy L lens throughout the entire zoom range, its going to be very expensive
hence in a bid to cut cost, i have a personal buying strategy of restricting L lens purchase to telephotos only. for wide angles and normal (50mm thereabouts) focal lengths, i strictly do not buy L lens. so u will have more $$$ left to play around with a wider variety of non L lens at short focal lengths.
example: instead of spending $1000 to buy the EF17-40L , depending on your dslr's crop factor, you could have bought EF24-85mm along with a EF50mm/1.8 and still have a few hundred dollars left either to save or spend on something else
the other time i saw one guy buy a 30d and 24-105L brand new straight from TCW. he paid about $3500 on the spot. i was thinking for about the same kind of picture quality that could be procuded, he could have bought a used 20d lying on the same TCW display shelf and a 24-85mm..total cost would be $1600. thats a $3500-$1600 = $1900 dollars difference:think: