We've been with them for 10 months now after starting out on ADSL and they've definitely come a long way.
Initially had a number of unexpected outages at inconvenient times but seems to have been rock solid for a while now and speed is better than their 'budget' pricing indicates.
We also have a server colocated with them, no issues.
If your customer is looking for a home connection then definitely give them a shot.
Business... maybe... if they need proven reliability it might be best to point them towards Snap/Unleash at this stage.