I've got a 07 E90 328i and I had to get mine done twice in about 3 months. I've also got Coverage One so it just cost me the deductible the first time and the 2nd time was under the dealer's warranty on the parts install. They figured the first gasket had a nick in it they missed or something. $1100 is really pricey, mine was $80 parts and $616 in labour. Total was around $800 incl taxes.
I'm surprised the valve cover gasket is still an issue in the E90. It was a problem with my E30 and 17 yrs later, it's still an issue.