I use them from time to time, but mostly because i love how they look and work, the shock cloaked one is my favorite, weird since i hate spiders IRL but this guys just look awesome, and i see them as sort of pets, i never spawn a bunch of them at the same time, i often have only one, they get annoying sometimes because they are slow and i have to stop to let them keep up, and they are glass cannons, once they get hit they will die in short order, but as long as the enemy is focusing on you they can just drain him of HP so fast, even high end enemies like Draugr deathlords will fall within about 10 seconds, i even tend to keep enemies alive and fight defensively just to see my spider take them down, i just had a big mayhem in Whiterun and got my spider to kill all the guards by casting heal other on him repeatedly.