Having enjoyed the integration between Lightroom 3 and Elements 8 on Windows 7, I was expecting to find the same on Lion.
By default it didn’t work! Trying to open a picture from Lightroom just ended up with the Elements prompt to Edit or Organise, and clicking on Edit resulted in no photo.
The secret is to use just the Elements Editor! There is a single application which you can see in the picture below. Open with this and it works just fine. As a bonus I can open the Editor directly as I don’t use the organiser in Elements.