[TeeWEE]

This depends on your target users. If they only live in the Netherlands for example you have to target different devices than USA or China.

Testing on a few devices across the dimensions (resolution, dpi, cpu, manufacterer, keyboard[less]) then you are pretty save.

But I have experience where we tested on a range of devices, but the app still had problems on 1 or 2 specific devices such as the sony ericsson xperia mini.

So if you have the money I would recommend something like testdroid to be increase your testing confidence.