I'm cheating today. Sorry.
I saw Limitless last night and wrote an extensive review for Media Matters (Third Way Cafe). As soon as my review appears online (soon), I will put a link here to that review.
Here is the link: http://www.thirdway.com/mm/?Page=6268_Limitless
In the meantime, I will say that Limitless starts very well and at the midway mark I was still completely engrossed. But the second half deteriorates quickly and the film ends very badly. Because of the intriguing premise and good first half, I am going to be very generous and give Limitless ***. My mug is up but while those first sips were tasty, the rest got cold way too fast and what's left on the bottom is best left to your imagination.