Unfortunately there is no ending...if he woke up from a coma or was in a future like the Matrix it could have worked.
Of course, if you were a killjoy, you might ask yourself why this cognitively enhanced, super switched on guy doesn't seem to devote much of his energies trying to find out where the next stash of NZT is coming from. He seems to go through the whole film running out of the thing. Or why he can't seem to free himself from the clutches of the Russian loan shark. I'm almost tempted to rename it Limited. 3 stars
I give this a 1 1/2 star simply for one scene: the hero's girlfriend takes a pill in the second act and 'thinks' her way out of the situation. This scene alone is worth the price of admission. Brilliantly written, filmed and edited. Unfortunately, it comes so late in the movie that it's almost impossible to care. The rest of the film is over-shadowed by this singular scene...
I rented this dvd to watch after I read the reviews for Lucy, another film with a similar plot. However with Limitless, I found myself incredibly bored from the beginning and had to pause it, and do something else. I went back again to try and finish it again...and again...and again. I did my best to not watch it on fast forward, which is the death knell for movies that I rent or stream. It took every bit of my 24 hour rental to get through this thing. I can't say I speak for everyone, but a movie experience should be a fun occasion, not a struggling ordeal.
Watch Lucy instead. That is another flawed film but it succeeds where Limitless fails: Lucy is at the very least funny, unintentionally so. I laughed my ass off watching Lucy, but Limitless gave my eyes a workout...they were either constantly rolling or watching the clock hoping it would all be over soon.