I think it's too early to say if there's an impact on litter yet. It's only been a few months. I do volunteer litter picking in my area and plastic bottles are part of the waste but mostly it's other stuff, so I don't think it will make a big difference.
We have kerbside pickup so now it's just made it either more expensive or more hassle... I hate it. People who were already recycling will be the ones who bother to keep another bin for just these returnables and then go to the shop to put each one in the machine individually, then get a receipt, then go to the shop to redeem it for money. It's a huge hassle and the machines are a waste of energy and ugly.