That was one of the other complaints I had with Medicare. My employer insurance (Blue Cross Blue Shield of IL) paid the day after a claim was submitted if it was submitted electronically. Also, their website was easy to understand with a good user interface and if I had to call them, everyone was knowledgeable and friendly.
Social Security Administration/Medicare on the other hand? Interminably long wait times on the phone, get a different answer every time you call. They lost one of my payments so I had to loan the SSA an extra $700 for months while they tracked the payment down. I kept apologizing over and over to my different providers telling them that I had to be on Medicare so they were going to be paid slowly as I wasn't going to pay my share until Medicare paid. And their website was complete garbage from a user experience standpoint.
I guess if I didn't have such stellar employee insurance, I would have been happier on Medicare. But at the time, it was a definite downgrade.
Insurance companies seem to be very keen on the laws and what they have to pay and not pay. But they are also fairly quick at paying their share whereas Medicare is extremely slow and months and months behind.