I purchased my first iPad last week. I bought it for the purpose of developing iPad apps. Why?
In the last three months of 2011, Apple sold 15.4 million iPads. A lot? Yes. Current trend? Upwards. Way upwards.
Buying apps on an iPad is mostly an low-friction impulse purchase.
An iPad is expensive. Someone who can afford an iPad is likely to have a reasonably high level of disposable income.
There are many iPad apps already, the vast majority of which earn little to no money. This is because developing a simple iPad is just challenging enough for a software developer with a new iPad to enjoy, while being just easy enough to complete. However these developers usually don't realise that running a successful business involves more than just realising a simple app, then sitting back sipping cocktails on a Caribbean beach. A successful business requires skill, persistence, and luck.
My feeling is that if I create some apps that appeal to people, then listen to feedback, and improve, improve, improve, this can be a viable business. Does it require some luck? Indeed. But it also requires business skills, software development skills, an ability and willingness to continually learn, and the secret ingredient: persistence.