I?d like to add my 2 cents in this interesting discussion about winter feeding. Richard says that sucrose is the best because it is clean, pure, produces little defecation, etc., and that countless scientific studies show that it to be so. Michael points out that sucrose induces stress and that, in stressful conditions, honey is better. After all, after millions (not one but very many) of years of evolution bees would probably have hit upon sucrose as storage material if it was better. My point here is that there are many more factors to consider when evaluating honey vs sucrose than nutrition. Even regarding nutrition, sucrose is deficient in a number of other nutrients than honey (minerals, vitamins, certain other cofactors, etc) that bees require. Besides, sucrose simply can?t be stored over an entire winter (a very important concern during evolution I?m suspect) . It is only a good food because we, humans, give it to them and clean up the mess it makes (i.e. fungi, etc) or replace the feeder often enough. There is the additional pH element that I would venture (not knowing what a bee?s stomach ache feels like) is not necessarily a big deal. After all we too can eat lots of oranges or yoghourt (at a pH close to 1) without much problem ... but then again would not just feed on oranges all winter long!
Then Richard argues that natural is not necessarily better and points modern medicine as the evidence. Here again, at first glance it look like an unbeatable argument, but I would argue that the benefit we reap (in terms of quality of life and longevity) is very short lived (in evolutionary terms). By saving the life of many people now who would not have othewise survived in the past, we AS A SPECIES are becoming very weak: many undesirable traits (or genes) are being passed along to future generations, that we simply can?t foresee the effects of in the long run. Plus, thanks to the increased longevity, we are amassing enormously large populations that are destabilizing the whole planet we live in. So, benefit for the individual (which I obviously appreciate) does not necessarily carry benefit for the species and has therefore unpredictable evolutionary value. Also, lots of investigations indicate that bugs are winning the war over humans: they are almost infinitely variable and will always find a way to outsmart scientists and modern medicine (consider for instance the many new strains of drug-resistant bacteria, viruses and weeds). We may beat cancer but something else will show up to haunt us. Also, the way of life that these advances allow and promote generate more stress and consequently new conditions for bugs to strive (much like stress-induced bee diseases).
So, sucrose may appear better for a beekeeper, but I think scientists are not necessarily considering all the factors, and it may be a very short lived benefit. Over long evolutionarily important scales (which may be only a few decades for bees), I would predict that feeding sucrose will generate potentially week strains of bees and strong ones of mites and other bee predators.

Jorge