A couple of things to consider (and this would apply to most small tablets, not just the iPad Mini):
Tablets are more often for consumption of media/data than for creation. Whilst there are a number of things you can do to create media on a tablet, if you need keyboard/mouse - for example long documents - then a netbook/laptop is better.
A small tablet can usually fit into a coat pocket or small bag, making them much more portable than a netbook or laptop, which means you can get online wherever you have a connection. If you buy a wi-fi only version you're restricted to places where there's open wifi. If you get one with a SIM card, you'll have a connection wherever there's signal. Personally, I find this to be incredibly useful because you can browse the web, connect into work cloud services, watch TV, browse the web, and more pretty much anywhere.
I have a small laptop at home, which I still use a lot, especially where a lot of typing is involved, but I also carry my tablet with me most of the time, and I use them both for different things.
You should also get more hours of battery life from a small tablet than you would from a netbook without the need to take along a charger.