I was with Titan from July 2008 until May of this year (2010). This time included Titan reselling me services from Entanet, Obit, and finally Vispa. What started out as a great service with Entanet declined with issues such as throttling and lower speeds. I agreed to stay with them as I naturally like to give people a chance.
To cut an extremely long story short, the service was never the same again, with long periods of downtime an debilitating speeds, particularly after the switch to Obit, and again around the switch time to Vispa. I agreed to be one of the first customers on the new service, but that ended up in a fiasco with little to no internet for over a month.
The worst thing about this company isn't that the service is patchy - rather it is when things go wrong they don't answer the phones. First it was at the time of problems with Entanet that they said there was a BT fault that lasted several weeks. More recently I have been unable to raise them on the phone over the last nine months, with well over a hundred attempts at different times of the working day. The message has changed from one about a fault to saying that they are busy, and it has no opportunity for call queuing.