It's hard to like Dave Burdow in the beginning (because of the whole Mary thing, plus we're Team Creighton in general), but then he does Jeth a solid and steers him clear from Wortman's trap. It's hard not to warm up a little bit to the guy after that. But then Dave goes all awesome again and donates some logs to help rebuild Matt's barn, making it pretty much impossible not to like Dave Burdow. But maybe that's the point.
Jethro reacts to his primary encounter with Dave Burdow with "a loathing that was new to him" that brought on "a great unrest inside him" (5.71). It goes without saying that Jethro is not a fan. But after the Wortman attack on his ride back home from Newton, Jethro becomes aware of the fact that he "clung to Dave Burdow's arm" (5.1 80) in all the excitement, suggesting that Jethro's sentiments toward Burdow may be shifting a bit.
By the time Ross Milton informs Jethro that Dave donated the logs to rebuild the Creighton family's barn, Jeth is resolute in his wanting to thank him, "one way or the other" (8.13). What's cool about this is that it shows us two things: Dave Burdow is not the bad dude we initially think he is (or if he is, he has the capacity to change), and Jethro is learning to form opinions based on his own experiences and is comfortable changing his mind. That's a lot of info to get from a couple brief interactions, right? Good writing can do that.
With the overtone of a country at war, it's easy to divide things into us versus them, good versus bad, and right versus wrong—but in the real world, things are rarely that clear cut. Dave Burdow's storyline exemplifies the complexities of human relationships on a personal level. Magnify that by a billion (give or take) and you get the complexities of war. Jethro learning to like Dave Burdow is the simplest example of how important it is to stop looking at someone as an enemy and start looking at them as a person.