Unfortunately this is another company that's fallen victim of its own success. Operating since 2002 they became very popular as Mike Holmes' plumbers of choice, and like other contractors that have done work for Mike in the past as their popularity soars their quality sinks.
I've used Express Rooter services in a number of occasions and their work was OK - nothing outstanding but no nightmares either. My issue with them started in the last service call. A simple drain cleaning job. The plumber came did their thing and left. We thought the issue was resolved but when we called a couple of weeks later to say it wasn't they wanted to charge us in full again - what happen to your warranty?
On their website they say their work is guaranteed but in my experience IT ISN'T. Just like many other companies, once they take your money you'll never see them again - interestingly enough, the same companies that Mike Holmes tells us to stay away from.
I won't be calling these guys for my next job - they're become too big and unreliable now. As for their warranty: it's non-existent