Last week I went through our phone bill, penny for penny. I thought that switching to Verizon's new(er) data plan would save us money, and it turns out it probably won't. We also realize we aren't getting an employer discount anymore, because it expired. Verizon notified us of the expiration through an online statement, so this got missed. This is probably smart on their end, because it'll make them more money.
The biggest thing with breaking down the bill is that it'll help monitor upcoming phone bill costs. The phone bill should be pretty consistent month-to-month, but it hasn't been. This has been due to phone upgrades and activation costs. If the bill is higher next month, I'll be able to quickly tell where this cost came from. I also consider this important to not be "nickel and dimed" by Verizon.
Verizon's website was better to navigate through compared to previous attempts, but it's still not perfect. Keep an eye on your phone bill and you might save some $'s in your pocket.