Dedicated Mobile Hotspots: Are they worth it?

Do you use a dedicated mobile hotspot (like a Novatel Mifi) for internet access on the go, or do you use a tethering plan with your smartphone?

I figured smartphone tethering has greatly reduced the need for dedicated mobile hotspots, so I am curious if anyone still uses them. I've heard people with unlimited data plans love to use dedicated hotspots because they can essentially replace their home internet service with them.

Do you use one? If so, what do you use, and how has it worked out for you?