Well the end is a little ambiguous - frankly I was waiting for the yelling to begin. Because unlike Ianto, everything goes dark for Jack. So...if we assume that Ianto went to some kind of after existence (heaven or not) where did Jack go? Same place, different place, no place?

And all of Jack's lovers and friends from billions of year rushing by - was that his life passing before his eyes or the afterworld.

And if they are all together, I think the five men are having orgies...wait that would be six because Geoffrey would be there as well. Just think of the story possibilities there!

Confused yet? Me too. I just don't know about heaven as a physical destination or as a place where the 'soul' resides or whatever. So the interpretation of Ianto's and Jack's endings are left to the individual.