Dinan paid at least for one engine due to hydrolocking with their version 1.0 intake. V. 2.0 sports a proud nylon sock over the filter...
That said, I had an ECIS intake on my E46 330i and it was definitely better than stock: more surface, straighter path, got air from the same spots as the stock airbox (including the ram duct on top of the radiator) - and better sound.
Bought for $250, sold for $150 4 years later - amazing value. Let's see what becomes available for the 135 - preferably without acres of bare metal pipe exposed to the engine heat.