Poor throughput speeds due to congestion/overloaded service from Vodafone. My router syncs solidly at 74.4Mbs but throughput speeds have never been above 30Mbps from day one and are often between 2Mbs and 15Mbs. Tech support go through the same script every time and tell you that you have issues with your wifi, despite me getting the same speeds when using an ethernet cable. Throughput drops out several times per hour, however the router remains sync'd.

Their "speed guarantee" is ONLY on sync speed, which for this package is 55Mbs, so as far as Vodafone are concerned, the issue is after the router, i.e. our wifi and ethernet!

My neighbours on both sides are with BT and have similar sync speeds to mine and get minimum throughputs 50Mbs+ at peak times, so that rules out any issues with our local exchange.

As with all things, it's cheap for a reason!

EDIT:
From sheer frustration at the 0.6Mbps speeds today, I have just factory reset the Vodafone Connect router. I now have 30-40Mbps of ACTUAL THROUGHPUT. How long this will last remains to be seen...