Do lots of people get diabetic retinopathy, or is it unusual?

Not unusual. Retinopathy is one of the consequences of uncontrolled diabetes and is one of the most common causes of blindness in the US.
Very common. Diabetes is the leading cause of new cases of blindness among adults aged 20–74 years. In 2005–2008, 4.2 million (28.5%) people with diabetes aged 40 years or older had diabetic retinopathy, and of these, 655, 000 (4.4% of those with diabetes) had advanced diabetic retinopathy that could lead to severe vision loss.

Related Questions

Do a lot of people get diabetic retinopathy?

About one-third. The incidence of diabetic retinopathy is about 1/3 of diabetics according to government statistics. The condition is related to how well the diabetes is controlled and if you have controlled any tendency toward high blood pressure. Take care of both of these conditions and you are less likely to get the retinopathy.
See below. Uncontrolled diabetes mellitus (high blood sugar) causes the retinal vessels to leak. This leads to swelling and bleeding and scarring in the retina, and is a major cause of blindness globally. This requires the help of a retina specialist for treatment.