So yeah, it is confirmed that BF3 is going to have semi, burst, and auto fire modes for the guns for which it applies (all three for M16), and if you watch that vid you'll notice that there are different reload animations for inserting completely emptied vs partially emptied magazines like there should be. Oh and after he reloads after a partial mag, notice that there are 31 rounds total available.
I'm not saying that these things are ground breaking features or are back-of-the-box bullet points, but it's nice to see that they're not cutting corners like with the Bad Company games when it comes to weapon mechanics.