I've noticed it big time in the northeast. I live on the road and work via a Verizon connection. Over the last 6 months over 7 or 8 locations I get a full Verizon signal (with a booster) and very low speeds compared to a year ago. And speeds increasing at off peak times (it's fast in the middle of the night) point to overloaded towers.

I know people love to hate on cell companies but it must be hell to try and keep up with demand that changes so rapidly.