I hesitate to answer this because it seems so emotive to so man people. But I've been using mainly non-lead cartridges (steel and bismuth) since I started wildfowling in 2007, and the shoot syndicate I'm now in transitioned to exclusively non-lead four years ago. I haven't used lead for years now, and the same goes for my stalking rifles. In practical terms, it makes not one jot of difference to lethality. Steel shot tends to go right through birds or stop hard up against a bone, so in that sense it performs differently from lead. But certainly family and friends are happy to hear that none of the game I feed them contains lead. As am I for that matter. I don't really know whether there's a danger to human health from ingesting lead shot, but since I don't have to, why take the risk?
In terms of shotguns I did buy a new one 3 years ago, but before that I was using standard power steel in my old Brno side by side with no problems at all, and sometimes bismuth in my 16 bore. Bismuth is punishingly expensive but I look out for second hand cartridges or auction clearouts etc, and I don't use much anyway. Steel is a bit more expensive than lead but it's actually a pretty marginal cost in the overall picture.
Finally, it's not like this is a surprise to anyone. Fighting is a waste of time and energy. Did some of you fight the switch to unleaded petrol back in the day? It turned out fine in the end. It will be the same with this. No-one will remember what the fuss was about. As someone who has already fully transitioned, just embrace it, it's fine on the other side. Stuff changes, we adapt, that's how the world works.