I worked in Geneva for three months in 2011. There are wristwatch shops in abundance, as well as a couple of good shoe shops, but otherwise it's not really a particularly good place for shopping. When I was there, the strength of the Swiss franc meant that most locals travelled a few km over the border to France, where everything was way cheaper. However, there is a really excellent food hall at a place called Manor, halfway between the railway station and the lake.
As for eating out, there are plenty of good places, provided you have an expenses account - reckon on £100-150 for a modest dinner for two. There are some fun open-air places down by the lake, and also in Carouge, a slightly Bohemian district just to the south of the old town.
Frankly, if you're only there for three days, forget about buying clothes. Take a trip up Mont Saleve perhaps, to enjoy the views of Mont Blanc, Geneva and France, or take the mountain railway from Nyon up into the hills north of the lake, or just explore the old town area of Geneva. It's very easy to get about, either on foot, by tram, or by launch. If you like French films, there are plenty of cinemas there.