I don't think any single poll is reliable enough because they all have some sampling bias. For example the recent AP poll was weighted incorrectly because it polled an unrepresentative amount of evangelicals, which tends to favor Republicans. It's probably best to take the average spread of polls like on
http://www.realclearpolitics.com/polls/
The polls are just general snapshots. I guess the polls that really matter are the state-by-state polls because it's whoever gets enough electoral votes that counts.
People are saying it'll be a landslide. It may or may not be. I suspect Obama will win some battleground states but also lose some. Being ahead within the margin of error means it could tip either way. One thing that seems to be playing in Obama's favor are reports of record Democratic turnout among early voters.