Helmets can be very subjective, and doubtless you can be unlucky and get a bad one (like the last reviewer), but I have to say my experience with the BMW Sport helmet has been very different.
I purchased the white Metallic one from John Clark BMW over the internet for the reasonable price (at the time) of £229.

First off the helmet is very light at 1375g, and it feels it. Provided the chin pad is fitted I also found the helmet to be extremely quite, certainly the quietest helmet I have ever owned (previously owned Schuberth C1, Airoh, AGV, Bell, NZI).

The anti fog visor insert also works a treat, never fogging up, The ratchet chin strap mechanism is very good, feels secure, but is easy to open and adjust.

If you wear glasses a down side is that they will fog up with the chin insert in place, and without the chin insert I agree the helmet does become more noisy and drafty, (but about normal I would say)

So far after two years of use, nothing has broken or fallen off, although just ordered a new tinted visor and the price is pretty steep at €70.

Without doubt BMW’s Sport helmet has to be the worst helmet I have ever purchased. I decided to buy what I thought was a good brand and make of helmet (as I’d previously had a BMW helmet before, but not the Sport) but it didn’t take long before I realised that I’d made a grave mistake. The noise from the chin vent is astounding and uncomfortable and there is an accessory that comes with the helmet that slides around the chin area to help prevent noise/turbulence, yeah right.

The visor, when in the semi open position, rattled more than a rattlesnake’s backside on heat. The padding inside is so badly designed that the top most pads insisted on vacating the premises whenever the mood took them. The air vent, just off centre to the crown, came off for no apparent reason, and said vent is now permanently open.

All this for around the £270 mark, it may have been more but I’ve really lost interest, but even the £270 is still an extortionate price to pay for this noisy, cheap feeling made rubbish. Leave well alone. You’ve been warned.