As far as I know The Affordable Care Act (aka Obamacare) focuses on the attainment of insurance, penalties to individuals and businesses that forego health insurance, etc. Pre-existing conditions (which would include mental) will not preclude you from enrollment I a program, and as they do many years not necessarily related to the ACA where mental health visits are not limited just like other medical service drs aren't generally limited.
I don't really see how it would prevent access to or use of mental health services - unless something happens to your insurance (giant company cuts you to 28hrs to avoid providing insurance,etc but they've already been doing that since the beginning of time).
Anyway... That's as far as I know. As far as cost changes, insurance companies main goal is to make money so your premiums may go up (but weren't they going to anyway? Mine do every year
).