This lock does an excellent job from what I can tell. Ever since I have started to use it, it does not seem that anyone has tried to take my bike. The long chain allows me to double loop the chain through my tire, so that is nice. I park my bike outside and it rains moderately here so I have seen a level or rust start to build on and inside the lock mechanism. Therefore it has been a bit hard to get the thing to unlock at times but I'm sure this can be fixed with some good cleaning.
I've had mine for about six months now. Comes with spare keys which is rather handy, but be sure to get a reminder cable. Mine did not come with one. It's really easy to forget you have the lock on w/o a reminder cable.
You might also want a pen light or something similar if you are using this in a dark area. It can be a mild pain to put on in the dark. Easy to take off however.
I would rate this as 5 star except the lock no longer requires the key to go all the way in to lock/unlock. This gives me some concern about how pickable the lock is.
I checked this out originally and thought it was OK. But I moved on to a different, more flexible item - a carabiner lock with a pretty tough 6 foot cable - good for a helmet and a jacket (or 2 helmets I guess). Don't know the brand (BigPantha) but it works nice