It is my opinion that Fringe did a very good job with this episode. It did feel introductory somehow, but it is a very smart move when you got a show that got a lot of buzz during the summer because it attracts new viewers.
The thing that I love the most about fringe is that it evolves with every season and, in my opinion, always for the best.
These characters are finding themselves once more, recreating and changing themselves. We cannot expect to se the same Olivia, Astrid and Walter interaction from the previous three seasons because Peter is just gone.
So, all in all, I think this was a great season openner. Very excited to see what's to come.