I used the Army Painter metallics, and I personally thought they were miles better than their other colours in terms of how thin and smooth the paint was, and how well it went on. They smell more strongly though, and they took much longer to dry (although I leave sprayed models overnight anyway, but still...). One more thing I should mention; I put a spray primer of Halford's grey on all my models first (again, dried overnight for a full cure).
Generally though, I would recommend looking at automotive sprays for metallics - they are specially designed to be tough, to go on thinly and adhere well, and to stick equally well to metal/plastic/putty, and are normally very good value compared to miniature paints/sprays. Some will be glossier than others though, especially as most car sprays are designed to be used in the following order: primer > 1-2 coats of the colour spray > clear coat. Obviously, for miniatures, that can be a bit thick, so I just do: primer > 1 coat of colour, and then use regular mini paints on top.