Viper is what I would describle as personable & outgoing -- he is always the one making jokes, pushing people to better themselves as a teammate (even if that isn't always readily apparent), and really he does try his hardest. I think that he is capable of doing great stuff if he continues to apply himself as he has; he has definitely come a long way from when we first met.
An area that I think Viper tends to struggle in -- and I think he fails to notice repeatedly -- is when given criticism, he really seems to struggle to put it into action-able, practical plans...which can be frustrating for not only you as a teammate, but unfortunately him himself, which is where I believe he had attained a rep for getting angry in the past. Whether this manifests as him changing the subject, or something like 'I don't know what to say', I have noticed in the past that this quality has had a negative impact on his performance. I think that if he is able to overcome this hurdle, he really would be right on the beaten path to becoming an extremely good soldier.
Overall, Viper is an extremely good friend with an extremely positive attitude. With the right enviornment and a team that can keep him focused, this dude really is capable of some nutty shit. give him a shot!!!