I've had the H&R Springs for a couple of months now and they a good spring option. The lowering is lower than Eibach and ACS which I like, but that's personal preference. Technically, I personally think the H&R aren't low enough as it still leaves a visual gap between the fender and tire, but again...this a personal preference.
The ride is good, especially considering the amount of lowering. Handles better than stock and by no means is stiff. It can be a bit bouncy in comfort mode, but in sport or sport+ it's perfectly fine.
To put my viewpoint in perspective, I come from an E46 M3 with Clubsport coilovers, and feel that my F10 handles decently for the size of the cat. I also do drive my kids in the F10 with no complaints.
I will say that I am switching to KW V3 coilovers, but that's partly due to achieving my ideal ride height.
'12 Alpine White F10 535i ///M Sport