I finally bought a slanted liner brush at IMATS and it was definitely worth it. There isn't much difference in the final look, but the ease of application makes it a useful tool. I credit the difference to 1) the slant of the brush and 2) the synthetic bristles (think the kind of bristles your toothbrush is made of). The gel glides on easily, and doesn't get stuck in the hairs of the brush. Applying is much quicker and I make fewer mistakes.
In sadder news, my Shu Umera lash curler is STILL missing. I am using my old E.L.F. curler. I really like the curls I am getting, but it's pulling out my lashes. Annnd I just bought Shiseido refills for my Shu, so they're just going to sit there. Boo.