He's a good hockey player. He's not physical like you sometimes want from a 4th line player, but he's sneaky dirty, which could be useful in the playoffs.
Sometimes these deadline rental deals don't work out. In the meantime, he has to be considered among the best 4th line centres in the entire league.
I would have liked to see him play 1000 games with Montreal. In a season this bad for Montreal, however, the return was too good to pass up. It's nothing great, but you take solid value wherever you can find it. And it looks better seeing all of the non- other moves Montreal made.
A small thing I liked is that Bergevin tried to accommodate Plekanec. According to reports, whatever they are worth, he didn't want to go West. Winnipeg had made a comparable offer. Bergevin tried and got a similar enough deal from an Eastern team. Small thing, but I think it counts for something.