I've been playing it every night almost since I got it. It's incredible! The frequent save points give it a good pick up and play option, but as soon as you get into the atmosphere, its hard to put down b/c you keep wanting to see just a little more. If someone had more time, it probably is a 3-day run thru.
But yeah, buy this new to get the code and support the dev's this is really only their 4th major game in over a decade. I just read in the GI Afterword for this game that they have a lot more content past the DLC, so it sounds like a new sequel is a definite possibility and will probably just use the same engine, hell why not?!?