He's no coward. It took a lot of guts to do what he did. He might be selfish but it's not cowardly to join a team that you think could be one of the best ever.
The whole argument about not staying on the same team like Magic, Bird and Jordan is ridiculous. If Lebron had a McHale, Pippen or Kareem on his team he probably would have stayed. He had a Mo Williams, Andy Varajao and JJ Hickson.
After seeing Dan Gilbert's reaction can you blame him for leaving? The guy is a thankless nutjob who has probably ruined any chances for Cleveland to get future free agents. LeBron gave a lot to that team, basically carrying it for 7 years, and that's the reaction? Some of it was justified but it was done in a totally classless manner.
LeBron's "show" wasn't so classy either, but I wouldn't call it cowardly.