Yes this is one of my favorite games. It's worth at least 2 playthroughs I'd say, and I would love a sequel as well.
However, this company is brilliant. They are the same that made Fahrenheit/Indigo Prophecy - it's about as good and original as Heavy Rain (more nightmare/horror perhaps) but might be a little bit outdated in graphics at this time (I'd just really recommend it if you love HR anyway).
What I mean is that, whatever they are making in the future will almost definitely be awesome, so it's OK - while they could make a bunch of sequels to this game very profitably - they have the "We want to do something new" attitude, so they're not making a franchise and milking it which is imo often a very good thing