Yeah, it's a great game to replay, not only to see the different ending, but also it gives you a chance to experiment with a different play style. You tend to get comfortable with a particular set of tonics, plasmids and weapons, so it's good to mix it up in your second run through
There's actually 3 endings to the game, but 2 are very similar. There's the 'good' ending (save all the Little Sisters), the 'bad' ending (harvest most/all of them) and the 'sad' ending (harvest a few, save the rest - I'm not quite sure what the cut-off number is though). The bad & sad endings are exactly the same, but the voiceover is read with disdain or sadness, respectively.