I have several pieces of computer equipment that I wanted to keep locked up with a cable (desktop, backup harddrives, 32" LCD TV, etc.) due to my paranoia about break-ins in the area. I have nicer cables for my computer and TV, but couldn't see spending $20+ each for cables for my other equipment (hard drives). So I got 2 of these cables to try out. They seem to work well enough. The cables are relatively short (3.5') and that's perfect for what I need. The locking 'fingers' seem to extend pretty far, so they hold into the lock slot well. It was a bit of a snug fit into the lock hole on my iBook (2001), but on my iMac and hard drive, it went in pretty easily (just trying it out on several things before writing this review).
I can't comment how how these will hold up for daily use, like in an office situation where you might be locking and unlocking your laptop every day, but my use is that I lock the device up once, and only need to unlock it once or twice a year.