it's worth the fix. The CHF is expensive and only available from BMW. I'd hate to be standing on the side on road with no pwer steering. Also a repair manual states the brake fluid and this is connected. I'm not sure why, but maybe the traction control ? This wasn't sure for me, but I remember reading about the ASC+T mineral oil cicuit (CHF) must be bled before the brake fluid. So I guess your traction control doesn't work properly when this fluid level is low !