I think it's 2 as well. I can't see any pattern/progression (but I got frustrated and didn't look for more than a few minutes) but came to the conclusion based on the consistency of vertical lines in each of the three columns. Based off that, the fact that you can eliminate 1, 3, 4, 6, and 7 based off too many lines counted in linear and angled orientations, leaving 2, 5, and 8 as the only options, 2 is the only one that fits the linear lines (the left always has one down, the middle has one always up, the right must have both one up and one down). In essence I didn't even need to look at the angled lines except for a basic count of them.
I could be wrong though, my "logic" is rarely what it's supposed to be, even if it "works".
Edit: Ok now I see the pattern. Going across the rows, the angled lines are only preserved in the last image if they appear in the same location in the first two images. Where as, the linear lines appear if they appear by itself (if it appears in the same location in both images it dissapears).
Aka: For rows, angle line duplications are preserved, linear duplications vanish. Going down columns this is inverted (angled line duplications vanish, linear duplications are preserved).
This would not be the first time I got the answer for something, had "strange and incomplete" logic, and then later on came to see the full logic/pattern. I never think in a straight line. As I like to put it "I don't think from A>B>C, I think A>Q>fish
".