I spent a small amount of poke balls. I seem to have trouble around here with getting different types of Pokemon, it's all repeats and I don't live near any stops really. Just convenience so I'm glad it's an option. I wouldn't spend more than ?10 on it, though. Think I'll just put up with things until I can replenish my stock
I have bought Pokeballs a couple of times when I was out and there was something I needed nearby. Otherwise no. I don't understand why people would spend tons of money on games they can play for free if they are patient!