You're getting some very one-sided views here! I may be tipping that balance, but don't mean to put you off, as I think they are great!
I like mine, have used one before and after having children for over 10 years.
But it's not clean! I have heavy flow now, and often have to empty it every 2 hours or so (but that's fine as I'd struggle to get tampons/towels to contain this), and I always use a panty-liner or towel as well. But often I can wear the same towel all day, so it is a saving that way. It doesn't leak as such, but you get a lot of blood on your vagina wall that is still going to dribble down, iyswim. Twisting it when you get it in seals it, and the only leaks I've had have been when I've failed to do this, or it's overfilled.
You have to be very body-confident, imv, to "cope" as you have to shove it a fair way up to get it comfortable so that you don't feel it, and then it is great. As you take it out, if it's full or near-full, you may well find it easily tips/spills, and you start dripping while you're managing this.... and you end up with a hand covered in blood. Not easy to manage if there's not a washbasin next to the toilet, or you're at a friend's house who has carpetted floor.
And when you empty it down the loo, the blood usually pools at the bottom of the loo, meaning you need to flush twice... can be embarrassing if there's a queue or whatever.
Coping in public loos - if you flush the toilet, there's clean water flushing in, can give a quick rinse under that if you're really stuck (like when I dropped the whole thing in the bloody - literally - loo).
It doesn't shorten your period (mine last about 8 days all in), but certainly when your flow is not really heavy (I have 3 days like that), it's great because you leave it in all day pretty much.
By the way, there are 2 sizes, before and after birth, and I did feel my before birth one leaked, so I gave it away and got the larger. I wouldn't use one straight after birth as you may be a little grazed in there and wouldn't even realise it. You'll not be big and flappy though - feedback I received 2 weeks after birth of 2nd suggested I was jolly tight!
Go for it, I don't think you'll regret it, but it's still a messy business. Emptying usually involves 2 handwashes for me.