Pros: Comfortable, crash tested, secure, cat is far less anxious
Cons: Expensive, accessories sold separate, no waterproof liner insert
The main idea of the Sleepypod is to keep the dome off at home so that your cat can use it as a pet bed and fill it with its "scent". Therefore when it's used for travel the cat will be be surrounded by its own familiar smells making travel less stressful. I have two cats and unfortunately the one who rarely travels decided that this should be used as a litter box and urinated in it within a week of me leaving it out. Some of the pieces are machine washable and the rest I had to use a cat urine cleaner and then rub baking soda paste all over to neutralize the odor. Even though I can't keep it out for my traveling cat to sleep in, he still travels in this carrier so much easier than the other. Prior to this I had a regular crate and he would stand up and meow and try to stick his paws through the door, but with this he lays down and curls up against the side. The dome is mainly made of mesh that is perfect for him to see outside a little without getting freaked out.
Getting him in is really easy because I just unzip the top of the dome (no need to take it off for this) and gently drop him inside. Then when we get to the vet I take the dome off for easy access (no reaching in to try and drag him out like with a crate or tipping the crate to slide him out) and when the vet and I are talking he lays down inside and I think he feels safe surrounded by the sides of the bed. Before he'd try and jump off the table and act extremely anxious. The inside is this nice fuzzy plush material that is perfect to keep him warm. If needed they also sell a warming pad you can stick inside (it's not necessary for me though). If it's warmer where you live you can also buy a mesh material to replace the plush to create airflow inside to keep them cool.
One of the biggest selling points for me is that this has two loops for the seatbelt to go through and is one of the few carriers out there that is actually crash tested. If you go on their website or YouTube you can actually watch the crash test videos and see how well this works vs other types of crates. This makes me feel a lot better when I travel with my furbaby.
The reason I gave this a 4.5 rating and not a 5 is for two reasons. The main reason is obviously the cost. I got mine for $179 on Amazon, but I think they normally run between $160-$169. I spent a little extra for the robin egg blue color (what's $10 more bucks if you're already spending that much). The other reason is that I wish they made a waterproof pad that I could slip inside in case of an accident. They have these inserts for some of their other carriers, so I don't know why they don't have one for this. I read somewhere online that if you purchase that mesh insert (that I mentioned earlier for warmer climates) it actually creates a small gap between itself and the bottom of the carrier. I think that someone cut up one of those indoor puppy pads into the shape of circle and was able to fit it in. I haven't tried this, but I think it's worth looking into. If you are going to spend this much money on a carrier you don't want to have to scrub cat urine scent out of it.
Overall I highly recommend this product. Also it's nice that both the vet staff and other pet parents always compliment it and ask questions about where they can get one. :)