If the connection is good and solid, and the drive caddy is fully seated in the rack you are good to go. Before your computer will be able to access this drive the rack must be locked down. This is done for two reasons, one to keep the rack from being removed when the computer is on, and two, to stop people from easily taking your harddrive.

 I suspect only the first one is really accurate though. A really cheap lock on the front of the rack mechanically stops the drive caddy from being removed, and also enables power and IDE signals to reach the harddrive. A small LED lights up when everything is working properly.

When you want to remove your hard drive from the rack, simply unlock the thing, and while your computer is off, lift up the handle and pull it out. At that point you can store your harddrive in a safe location or take it with you to another computer, so long as it has the same kind of rack.

The only downside to this rack is that if you have it out for extended periods of time, you are basically leaving a big giant hole open in the front of the case for dust to enter. For its price, it is a pretty decent piece of plastic, but I suspect if you were to ever experience problems with a hard drive, it could quite easily be traced back to this removable drive rack. And as far as protection for your drive, don't expect too much in the way of shock protection should you ever drop the caddy.

Otherwise, I'd have to agree that they kinna make any computer look a bit more 'powerful,' so maybe it's really just good image builder for your system.;-)