When it comes to choosing a soft-sided carrier, though, you have to be careful. I have one carrier that I absolutely love, which is the Sherpa Deluxe. The Sherpa Deluxe really has everything you could ask for in a soft-sided carrier: it's secure, has pockets, contains a washable fleece inside, and it's light-weight.
However, I have another "Fashion Pet" carrier that I bought first. I got it because it was cheaper than the Sherpa and it looked nice enough when I saw it in the local Petco. I could have sworn there was a picture of a cat on the packaging, though the last time I visited Petco I looked at the packaging and I only saw pictures of dogs, which is as it should be.
The Fashion Pet carrier and others like it have a "feature" which makes them extremely dangerous for cats and, honestly, if I were a dog owner, I'm not sure I'd like it either. Note the loose flap at one end of the top opening (top picture) and compare it to the lack of such a flap on the Sherpa (bottom picture). This flap is designed to allow your pet to stick his head out of the carrier and get some fresh air. In reality, it allows your pet to unzip the top of the carrier, even if the flap is locked closed and you don't want him getting out. My fiancee Liz and I found this out the hard way, by having a few near-escapes when we took the boys to the vet in it.
To be fair to the Fashion Pet company, there is a leash inside that carrier that you can attach to your pets' collar to keep him from jumping out and running away. However, I think most of us with cats would cringe at the idea of hooking our cats up to a short leash and I don't think even a dog owner would want their pet to be able to unzip the carrier when it's supposed to be closed. I think the least you can ask for from any carrier is to keep your pet from escaping.
So here are my words of wisdom: be careful when choosing a carrier for your cat. Make sure the zipper goes all the way around like it does on the Sherpa.