Tamum, I just had a look at the paper you linked to and I think it's interesting, but I would quibble a bit with the findings.
Can't access the whole paper so I might have missed something of course.
From the abstract it seems the parents were encouraged to bfeed exclusively for as long as possible, then the outcomes were compared. There was a higher incidence of allergies amongst the children who were exclusivley bfed for longer.
I do wonder though, whether all this tells you is that some children with allergies are more reluctant to take solids - ie allergies caused late weaning rather than late weaning causing allergies.
I do wish there was some really solid evidence about all this - would save a lot of arguments and hassle!