It has a few rare, but nasty, side effects that are unlikely to affect most who take it. Tardive dyskinesia is one.

It is associated with weight gain - that is one to look out for. I gained 70 lb in 8 months on another atypical antipsychotic, risperdal - at a low dosage. In the case of Seroquel, there is actually a label warning for hyperglycemia and diabetes. i.e. it can affect the proper functioning of your pancreas.

Side effects are probably most relevent to those taking the drug as an anti-psychotic at high doses. Taking a bit to get to sleep is probably not an issue, but keep an eye open ... esp. to weight gain. You should occasionally have a fasting blood sugar done to make sure you aren't in the hyperglycemic response category. If it was me, I would want one after one month and then every three months and each time the dosage was increased. You don't wan't drug-induced diabetes.