I recently cancelled MCI's Neoghborhood plan. While $50 sounded great for local and long distance, taxes brought my bill to $75 - $80. I live in Virginia and I am sure it varies state by state.
I had also signed up through Southwest Airlines and was hoping to get the 8 credits for using MCI. I only got 4 credits since I quit. No worries, it wasn't worth it for me.