The Good: Great new place to explore, lots of vicious animals to kill, a few interesting quests, two different endings
The Bad: Missions variety is lackluster, characters are developed well, area is a pain to navigate, very short, not much new content
It seems the New Vegas DLC just can't balance itself right. First Dead Money was full of cramped environments and brutal difficulty with game designs that worked against the game. Now Honest Hearts has a very open area to explore, but the characters are pretty underwhelming as well as the overall story. You meet some travelers who are part of a caravan trying to get across the Zion National Park and they hire you to protect them. Of course there's more than that so when you enter you see three rival tribes fighting against each other. You have the Dead Horses, White Legs, and Sorrows. The White Legs want to prove themselves so they can work for Caesar's Legion, but the Sorrows want to stay, and the Dead Horses are a rogue "extra" tribe. Of course know Fallout there's some sort of third-party hand in the pot and that's where Daniel and Joshua Graham come in.
Joshua wants to fight the White Legs and Daniel wants to run. Without getting into their back story too much you help each one out in various missions, but most of them are fetch missions and aren't very inventive. I was really disappointed with this and kept expecting some more exciting missions. Even Dead Money had some exciting missions despite its major flaws. The characters seem interesting at first, but after the initial dialog stuff when you meet them you never do much more with them. This is due to the DLC's short length running at about 10-12 hours. There are hardly any side missions, and it feels like the huge area gets wasted since you don't really get to explore it much.
The area is full of huge canyons and cliffs that surround a lake and a couple of rivers. The area is a pain to navigate because its hard to find how to get to high up areas due to all these layered cliffs. Some of the areas are great to see and they really captured the national park feeling with abandoned camps and cars in the road right when the bombs fell. So there is a nice charm about the area and seeing some trees and rivers is a nice change from the dried up Mojave. Other than that the environment is full of vicious animals instead of just people so that's also a bit different than the Mojave and Dead Money.
Other than that the DLC is worth a purchase, but don't expect 15+ hours and tons of new weapons or extra stuff. It's the best New Vegas DLC so far, but it's also not the best it could be. I hope the third and fourth DLC are a lot better and are finally on par with the excellent Fallout 3 DLC add-ons.