In my view, the answer to this question depends on the point of view from which we are looking at the issue.  From the point of view of the natives of the Americas, the negatives of the Columbian Exchange outweighed its positives.  From the point of view of perhaps everyone else in the world, the positives were greater.

For the natives of the Americas, it is very hard to see how you could argue that the Columbian Exchange was a good thing on balance.  The natives of the Americas got very little from the exchange.  They got horses, Christianity (which some would see as a benefit), and some technology, but these benefits were greatly outweighed by the negatives.  The negative impacts on Native Americans were tremendous.  The Europeans brought germs to the Americas and those germs led to the deaths of (in some scholars’ estimates) 90% of the natives of the New World. It is hard to imagine any benefits outweighing that particular negative impact.

For the rest of the world, the Columbian Exchange seems to have been mostly a good thing.  From an immediate point of view, Europeans and the rest of the world got corn, tomatoes, potatoes, and many other things.  At the time of the exchange, most people would even have said that tobacco was a positive thing.  For people from the rest of the world, the Columbian Exchange was only really a bad thing if you consider the Atlantic slave trade to be part of the exchange.  Outside of that, there is little bad to be said about the Columbian Exchange from the point of view of people other than the natives of the Americas.