I signed up in October, and have used the new insurance alot already. Got a colonoscopy (polyp biopsies benign), had two basal cell cancers (on my back) removed, and have had many costly prescriptions filled. And I've resumed seeing my therapist (dx: GAD and MDD.) As of this week, I've met my out-of-pocket max ($500) and deductible, so I'm "home free" for the rest of the year, confirmed by BCBSKC. Just for an example, an $800 Rx that I paid $20 for in February will now be a zero-copay.
My situation may be atypical, though, for at least two reasons. I had cancer at age 27 and again at age 43, so my medical needs are higher than most. The ACA brought my premiums way down after many years (retired in 2007) of paying very high rates -- not to mention no more preexisting conditions worries.
But also, I am lucky because almost all of my assets are, by design, in IRA's, so my MAGI is very low -- I'll have to do a modest Roth conversion each year just to qualify for the subsidies. But obviously it is a no-brainer to do so, and I am very grateful. Having added up the EOBs so far, I've easily saved over $10,000 already, while the Roth conversion will only increase my income taxes a few hundred dollars.