We've used Mr. Rooter a few times - from semi-emergencies to regular maintenance. The first thing you notice is the way they handle the visit. They give you an approximate time (last time we called it was a 2 hour window) followed by a call with a more precise time (last time it was 30 minute warning). This is great as you do not have sit aournd all day waiting, you just have to be reasonably close to home.
The last time we called it was to get a tap replaced. The plumber told us it would cost too much if he did it, told us how to do it ourselves for no charge.
We also used Mr. Rooter to replace our hot water tank and are very satisified. The work was done as promised, no mess left behind, the plumber was very pleasant.