My $10 stick blender (Walmart) has lasted forever. I think that's what most people use. What's nice is that it's save and doesn't incorporate air bubbles. I think you're much more likely to splatter with a KitchenAid type mixer.
Perhaps there was something wrong with yours? I'm not sure. Or you may be mixing too long. I also give mine a break and hand stir now and then. Most of my soap traces within 5 minutes.
That said I've hear people using mixers and even blenders. I still think a stick blender is your best bet. You could try a different or better brand too. If you're making huge batches I've also seen people using paint stirrers (like the pros use - it's attached to a drill bit or something)