my dog is slowly getting older and his energy levels aren't what they used to be, so i started seriously looking into this bag. i did a lot of research on this bag before i bought it. i read all the reviews, watched all the youtube videos, compared all the different models. like everyone else who has bought this bag, it's because my dog is my everything and i wanted to be sure that this was as safe and secure as possible for him. plus at $100, it's an investment!
after over a month of using it now, i can happily say that this bag is worth the money. you can tell it is well-made with high quality materials. my dog feels incredibly secure inside of it and just as important, he is comfortable in it. my dog has gone through a lot of different bags--baby slings, bags for the airport, etc. he hated all of them! he would fidget and move around to try and get comfortable, and it would stress both of us out. but in the k9 sport sack, he doesn't do any of that. he feels tight and secure and comfortable, even with the extra bag strapped on top of him. i like the mesh on the sides--even on sunnier days, he doesn't feel too hot (another problem i've had with other bags).
i got the plus 2 because it comes with the extra bag (perfect for water, dog and human treats, wallets, phones, etc) and because the straps are thicker and more padded. like the website says, this model is better suited for longer adventures. my dog is only 12 lbs but i'm glad i got this bag even just based on the straps alone. i haven't tried the air, but i imagine the pads on the straps make a huge difference! my shoulders/back are grateful.
not many of the other reviews i read acknowledged this, so let me just say very clearly that depending on your dog, it will take some time to get your dog adjusted to the bag. it is definitely a new position for their body (at least for my dog). my dog was very resistant at first (he likes to be free!) and it took a while for us to bribe him into getting in the bag (the youtube videos that k9 sport sack has are very helpful and i'd highly recommend them), and honestly even now (after a month). when i say a while, i mean we practiced for a while before even taking him on a hike. my dog is old so introducing new things into his life is a slow, steady process. he is still not very happy about being in the bag; that being said, however, he TOLERATES being in it! which is HUGE for my dog! just knowing my dog, i figured that he wouldn't be like some of the other dogs featured in the review who love their bag, but even my picky, stubborn, proud, senior dog can tolerate this bag because it's comfortable and he feels safe in it. so that's good enough for me. maybe one day he'll love it!
one small thing is that i didn't like the huge velcro on the bags; it feels like getting a patch is mandatory since if you don't have one it's just a huge velcro on both the attached bag and the actual bag. but this is small.
TLDR: this bag is high-quality, safe, and worth the money, though you have to put the time and energy in to helping your dog get used to the bag. even a stubborn and proud dog like mine will eventually tolerate this bag! and hopefully one day he'll love it as much as i do.