Here's my impression (not any speculation, just an impression, a review, if you will):
The People article had very cute photos and was a good interview overall. Good PR. On the Levi thing, Bristol hinted around that her and Levi were putting the past behind them and might even rekindle, etc... Maybe even think about marriage, although she said that nothing was definite.
Now, obviously, this article comes out on the exact same day that US Weekly announces they got engaged two weeks ago. Obviously, they work on these things a little in advance, so it's possible that she did People before the engagement. If not, then Bristol is a clever little thing. Maybe even a tad devious, but hey, she blitzes two publications in one day. You can't call her stupid. Also, there's the obvious thing that she gave US the exclusive, so she couldn't very well spill her guts to People.
As for the US Weekly article, I didn't read the whole thing because it would take too long and people were already looking at me funny for taking up the aisle reading a tabloid, but I did catch one line that I was glad to see.
I'm paraphrasing here:
"I love my mom more than anything. That'll never change. Once she sees that he's getting his education and has really changed, she'll come around and it'll be awesome. Until then, we're on our own."
Levi says something like he knows the Palins still see him as the punk who posed in Playgirl, but that was the old him. Um, yeah. Not much distance between the old you and the "new" you, Levi, but whatever. But he wants them to know that he really loves their daughter, blah, blah, blah...
Putting aside anything that may come in the future or any politics, I must say that overall the two pieces were good PR. Nicely done.