Been on Seroquel immediate release for about 5 years. Dosage has gotten slowly increased over the years and I'm at 600mg at night. About 9 of 10 nights it helps me get to sleep. That other night is just my worries that I'm allowing to eat me alive. I have to use legal botanicals to help that 10th night or I will be awake.
Here's the scary but. I am chemically addicted to Seroquel though. If I skip a single dose, I feel horrible for at least 2 days, even though I've taken the next dose on schedule and even though I slept anyway the night I missed the dose. That bothers me but not much.
As for depression, I don't think it helps, even when I started it for depression, in the extended release form. That felt like crap but I did sleep for about a month, which I didn't complain about because when I was awake I kept either contemplating or attempting suicide. That was a rough month. I ate maybe 5 times total. I made it through and with meds again adjusted the depression did finally lift, but I don't think Seroquel had anything to do with it. I think it was just bipolar 1 working its way through.