I have comcast business in DC, and have had since about 2002.
Every couple of years they "forget" our fixed IP address, and we revert to dynamic IP. The first time they did this, they tried to refuse to re-enable my old IP (they'd given my IP to someone else, who also ran a mail server on his connection, and refused all of my inbound email as 'no such user').
I have had three other clients with comcast business connections - two of them experienced the forgotten-fixed-ip problem; one has not.
My router has popped 2 - 3 times - they usually bring me a new one within a day or two, and sometimes they remember to reset the fixed IP address lease when they install the new router...
Overall:
- much better than they were 4 years ago
- don't use for 'mission critical' operations without a backup connection of some sort.
- as with any "affordable" internet connection -- if it doesn't work right away, cancel the order -- they will never invest any meaningful tech time to fix a single commodity connection.