I thought that after reading your other piece, I would give this a go.
I must admit that I enjoyed this one a lot more. The characters immediately struck a chord. Greg is fantastic creation. I must have sat in a waiting room with him on numerous occasions, Tim may need a tad of tweaking. Although he is a good contrast, I feel that he didn't really do that much to really ruin his chances. It would be great to see a little more length as Greg really riles him up to the point where he completely loses his mind.
I did guess Gregs true purpose very early on. I'm not sure why, I don't think it was anything in your writing but maybe another character, at least at the beginning would help to counter act that. I think that because of the situation we are presented with and the fact that there are only two candidate, its almost as if there is only one way to go. Nevertheless I still enjoyed the ride.
There are a few typos but I don't generally note those as its nothing a good once over won't fix.
One thing I have noticed is that you generally have a lot of 'ing' words. This is something I continually struggle with and always relay on others to point out. Go back over your draft and change all the 'ings' you can.
Great exchanges, this seems to be where you excell.
A little touch up and you have yourself a great piece. Perfect for a short with one location and minimal characters.