Moulson will almost certainly be flipped for more picks, so this isn't a bad trade at all.
Interesting theory. I guess the counter to that is that both teams already had a guy (Vanek or Moulson) that could have been flipped at the deadline, as I really don't think either team is going to the Playoffs. NYI is hanging in there now, but to finish top 3 in the Metropolitan division is going to pretty tough with that squad.
BUF absolutely fleeced them. Look at it this way: Could BUF had gotten a 1st, or possibly even a 1st and a 2nd just as a rental player in January? Almost certainly yes. So how does it make sense that they sold off Vanek as an early rental (which increased the return in picks), AND were able to get a replacement player for Vanek who is also a 30-goal scoring winger for the remainder of the season.
Crap, if that's how rentals work, EVERYONE would do rental trades. It's probably most likely that both of these guys test the market, especially Vanek, who everyone in Minnesota assumes is coming here next year (here we go again...). But Tavares and Moulson were really good together - I just don't understand what the end game is here for the Islanders. The Sabres have Ryan Miller in net, and Thomas Vanek couldn't help them be competitive on his own. If the Islanders and a 2nd "stud" youngster to go with Tavares, maybe they could be trading picks. But you don't ship out your 2nd best player along with the picks for a rental.