Careful with the word "promised". I've never seen that word used from Xfinity. The term you're looking for is "up to" when it comes to speed. I had a 250mb/ps connection before, should have been getting ~25MB/ps, never sniffed anything over 15MB/ps. Recently got dupped into upgrading to a 800mb/ps connection, went and bought a new modem to handle up to 1Gb/ps and STILL never see anything over, you guessed it, 15MB. If I do speed tests it'll test right but never a SUSTAINED speed anywhere NEAR what I pay for. Between that and caps it's really just a joke. Really wish AT&T would finish fibre in my neighborhood, not that they're any more honest but at least I'd have a viable option.