I haven't used ECS spacers, but I've used Macht Schnell spacers from EAS on my M3 and on my e70. The wheels I bought for my X5 had the 72 mm centerbore and the e70 has a 74mm centerbore, so I had to get 20mm spacer adapters and they work fine.
Looks better, in my opinion, as the wheels are pushed out 20mm so as not to have that tucked in look given the rear tires are smaller than stock.
I would think the ECS ones would be fine to use - I would not have any concerns about them.
Here's a pic with the 20mm spacers and bolts.
