The water heater in our home developed a small leak at the top an I felt it was time to replace it as it was about 10 years old. I didn't want to buy another one, so I got a new rental unit installed by reliance.
It was a forced vent gas water heater and when the technician came out he pointed out that our venting was no longer code and had to be replaced. However, the only practical spot he could run the new vent was covered by drywall and he refused to drill there because he said there might be electrical work behind it and he wouldn't wait while I did it. Long story short, I cut out a section of drywall in five minutes but had to wait two days (without hot water and two kids) for him to come back.
Once installed, it worked fine. One minor complaint was that when drilling through our siding it cracked and a two inch section broke off. The guy was honest about it and simply caulked over it. Also instead of properly capping off the old vent, as he ran out of caps, he stuffed a little bit of insulation into it and fastened a bit of aluminum foil on the end. The outside vent had a grill to cover it and it kept popping out. I fixed it myself with glue. Overall, an OK job with room for improvement.