I've had my Dyson Cinetic Big Ball Animal + Allergy vacuum a couple of weeks now and am still completely in love with it. I have to say I'm not experiencing any of the negative reviews I read/watched on it.
it's too heavy: Not at all. It's the same weight as my old vacuum by WAY easier to push/pull while vacuuming. The wheels roll easy and turn easy. It also has a nice handle in front to lift the whole vacuum.
it's constantly falling over and won't stay in upright position: Haven't had any problems with this. I push it up to the most upright position (last click) and it stays up.
the canister is hard to snap back in: no problems with this either.
I have tried some of the attachments. The tool for mattress and the tool for upholstery work well. The dusting tool: not so much. I tried it on my wood blinds, but the hose was cumbersome - every time I pulled back from the blinds the hose would suck back into it's original position and I kept having to pull to get it to extend again. It really doesn't want to stay extended. I found it just easier to clean the blinds my original way: with a swiffer duster.
Another complaint was that the dust and dirt didn't drop right out of the canister when emptying and you had to sometimes use your fingers get get out. I do have that issue, but it doesn't bother me. I think in my case it's mostly because it's long dog hair. If it was just dirt and dust it would fall out. It only takes less than a minute to clean it out.
I also like that the electric cord is very long. I used to have to plug in 2 spots to vacuum my house. Now I can just plug in the middle of the house and it reaches to both ends.
I love it so much I've gone from 30 years of vacuuming once a week to vacuuming 2-3 times a week!