I think in 07 the Hail had the Imprint 2 liner and no airbag in the sole (it was inside the boot) but it did have the articulating cuff. Since 07 the boot has been updated 3 times. They put a lighter sole on in 08 and added some anti microbial liner and gave it a full airbag heel. Then in 09 they gave it a new liner. Finally for 2010 they really went after it (and upping the price) with a "shrinkage" tech (giving a size 10 the footprint of a 9), airbag on the calf of the boot, and a midsole airbag (the 270 airbag cushioning system). So yeah, quite a diferences, but $50 is a great deal for what you got.
So what does all of that mean for a newbie? Is any of that stuff really a big deal? Or are these minor tweaks?