I don't consider ANY lock to be 100% effective. A lock is a deterrent. The thief has to expend time/effort. Hopefully enough that they move on to easier pickings. If they want my 40-year old bike that bad, they're going to get it. Or let's really get ridiculous and say you have a 16-pound weight weenie CF bike - and then you're going to carry around a 10 pound lock/chain???

Look at it this way, you can put ten deadbolts on the door to your house. Steel door, steel frame, yadda-yadda... BUT all it takes is one brick/rock to a window and they're in. Or just run through the wall - Yes, run. Vinyl siding over styrofoam with some fiberglass insulation, then a 3/8" wallboard. Yes, hitting a stud will slow you down, but then you know where the stud cavity is...