As much as I don't have a ton of faith in this team to do much in the playoffs this year, Boston is probably a better match up than Florida. Their record is deceiving - if the Leafs win tonight, they'll have the same number of wins, with the difference 2 or 3 RW and 1 or 2 ROW (depending on how the game ends). They'll also have a very similar goal differential (1 goal difference in Boston's advantage heading into tonight's game).
Overall, the two teams are fairly evenly matched - goaltending is obviously in favour of Boston, but offense is similarly in favour of the Leafs. Boston's defence has a good reputation, but the Bruins' possession numbers are all worse than the Leafs (and in the bottom 1/3 of the league, actually). Special teams does favour Boston, though.
If the Leafs can weather the forecheck at all, it should make for a closer series than I think people expect.