I enjoyed it quite a bit, especially the final two puzzles which did give me the 'a-ha!' moment.
For making the magnet feel more integral to the experience, I think it would be good to have to have the little robot be carrying it in order to (at least) enter a level, it felt weird chucking it away just to open a door. My first move in each level was always to pick up the magnet, even before I looked at the level layout, so if I was already holding the magnet when I spawn in, it might make me feel more connected to it as a mechanic.
I also think that rounding out the player's hitbox on edges may have caused me to think platforming, rather than magnet polarity, was the solution to puzzle six; all the way on the right of the level I could ride the magnet up to the platform with a two way switch, but I could also jump to that platform if I timed it well; that led me pretty far astray from the elegant solution of dropping the magnet, having it naturally slide down-left on the ramp, and only then jumping across platforms to the goal. It led to interesting emergent mechanics, like tossing the magnet on top of the blue (-) block and wedging it between blocks. I also tried tossing the magnet onto the 'pressure switch' at the bottom of the level and then jumping my way back to the two-way switch; even though it felt obvious that wasn't the right solution, I kept trying it thinking 'maybe this time I can get the correct throwing angle,' and reset maybe six times after tossing the magnet to a spot I couldn't reach. So in that stage the jump was just a little too forgiving; perhaps giving the area with the two-way switch a 'lip' might make it clear you can/should only be able to get to it via riding the magnet up.