I don't know what happened to the Waitrose that was meant to open in April 2008, or where. The first
Dubai Waitrose opened in The Dubai Mall November 2008. A second Dubai Waitrose opened in
Dubai Marina Mall January 2009. A bit smaller than the first one in The Dubai Mall, but appears to have mostly the same goodies.
Overall, Waitrose looks much the same as Spinneys (except the shopping bags are white and green instead of yellow and green), which makes sense since Spinneys had some sort of tie up with Waitrose anyway, and sold a few Waitrose products themselves. Maybe a few more goodies in the delicatessen counters. There seems to be a larger variety of bread but that might just be because they offer more tasting samples. Prices seem to be higher at Waitrose but that's an entirely unsubstantiated gut-feel estimate.