After FINALLY getting 3 gold stars in all levels of Path of the Jedi, I have begun playing the Hoth levels. The Hoth levels have a few new characters, most notably Princess Leia, as well as a few new game play elements, such as snow and ice, as well as giant snow walkers.
Princess Leia has some kind of pink tractor beam, which adds a small change to game play. As mentioned about there are some terrain changes, ice and snow. Ice will allow some objects to slide across it's surface, where as snow can be destroyed by impacting with it.
The Hoth update also adds a single additional bonus level (which can be unlocked without even accessing the Hoth levels) as well as one addition golden egg level.
One point of note is that at this time is that Hoth only has 20 levels, with the other levels to be unlocked at a later date. From the look of the level selection page, it seems that the last 20 levels may be set in an asteroid field.