Well....(Spoilers)
It was an entertaining movie but not necessarily good...still not sure if it was a true story or not.
The biggest issue I had with the movie was the portrayal of the clock on the battery. On almost every occasion that he left the room in the first hour he moved about extremely slow and seemed to be gone for much longer periods of time. It was hard to watch a guy go up 10+ flights of stairs and come back down them in less than 3 minutes...it's not even feasible.
They also seemed to focus on things that never ended up being pertinent later on like when he cut his hand badly.