yeah, i agree with the U-Lock suggestion...if your like me and tend to park your bike in the same place everyday...you can simply leave the U-Lock locked to the bike rack or whatever your locking to...then you don't have to lug it around everyday...or carry it with you on those days you plan on shopping after work
but i disagree with using a spanking new $1200 bike to commute with...use a beater with a couple cheap upgrades