Own two of these - one for my Samsung HDTV and one for my laptop and have had them for about 3-4 months now.
This particular lock is Kensington's (currently) most secure and advanced lock and on that information I chose to purchase this lock above all the others.
Yes, they are a bit more costly than the other one's you can buy but the main difference between this one and the cheaper locks is the lock mechanism and the keys - they aren't the 'circular'/'locker' keys that most of the other keys have but suposedly unpickable locks. The keys on this model are actually very unusual - they have 4 sides! However, scouring the internet before purchase, the lock on this is meant to be much better then the other kinds.
On that information alone using this lock actually makes you feel like you can leave your laptop somewhere if you need to without the worry of it getting stolen.
This lock might be more expensive than others but I would highly recommend it. It feels secure on both my TV and laptop and gives me such peace of mind (I actually use mine at university). Just loop it around a solid object and back through itself and then lock it up. Easy to lock, easy to remove (with the key obviously).
This is obviously only designed as a first point of defence against thieves - a determined thief could probably force the lock off but he would most definately have destroyed half of the laptop's case too. A good deterant then? then again, what thief wants half a laptop...
If you are worried about leaving your laptop on your desk at work, home or university buy this for peace of mind and trust me you will never be worried again.