I think that one obvious advantage to the polling process would be that it provides a solid read to candidates or elected leaders on the pulse of the public on specific issues. Polling enables the candidate or leader to not be trapped in a vaccum, in which they are absent- minded of what the public feels on a particular issue or idea. Polling is a way in which popular sovereignty is evident in that the voice of the people in the political process can be heard. At the same time, the divulging of polling information enables a larger discussion to be had about why the public feels the way they do and that reflects a discussion about the nature of democratic sensibilities, something intrinsically good.
The disadvantage of polling as far as I see it is two fold. On one hand, the polling science is not exact. Margin of error, conflicting sample populations, and the general temperament of people to change their minds are all elements that can change polls. There is not an exactitude to polling. It is a sample look at a general feeling. Yet, there is a tendency to deify the polls and live and perish by them. The idea of being hung up on two percentage points cannot be a fulfilment of the democratic process. At the same time, when elected leaders and candidates become victims to the polling process, something already inexact, discourse is not increased, but rather curtailed. If a leader or candidate refuses to do something because "the polling on the issue" does not look good, problems emerge. Finally, I would say that media deification of the polling process, again something inexact, creates even more challenge. Consider the exit polling process of Election Night 2000 in the state of Florida. Exit polling was revealed to be inexact when networks flip- flopped their call on the state of Florida based on exit polling. In this, I think that some significant questions can be raised about polling as used in the modern political setting.