I have used the Army Painter spray and like them very much. For myself, the key to using them and liking the results was not to use it as a primer, but rather as a basecoat. It is a little thicker than a traditional spray primer. But as a basecoat, it's perfect.
To me that's the whole point of the various colored sprays. Not as a true primer, because you can use a cheap primer for that and then brush on a basecoat. But to me the point of them is to quickly get your army basecoated with a nice smooth spray. Then all you need is to paint the detail on.
Just my thoughts on it.