I started EPIC, but found it too difficult to carve out the time, so I did EPIC Heat instead. I didn't follow it religiously - I run a couple of times a week, so sometimes subbed that in for HIIT, or did a day a day late.
I haven't seen a dramatic transformation (some of the people on the FB group are incredible!), but I'm definitely more toned, bit of arm/ab definition. I've put on, rather than lost weight - hoping it's muscle mass and not just my age! I was an OK weight to start with though.
I'm another person in their 40s concerned about bone density (don't want to turn into my mother!!), so that's a big motivator.
I think if you can see yourself improving, that's what matters. I could hardly do any push-ups at the start, and now I can do 10 or so in a row, and a couple of decent tricep push ups. I've just got some heavier weights - I did lower body with 6.5kg today, previously I was using 4.5. Not much compared to some people, but an upward curve for me.
As you say, different people find different things easy. I can squat/wall sit etc all day, but my core strength is terrible!