Ok, just talked to my plumber. These are the key points he to the half hour lecture he gave me but time for me to eat some crow

1. He doesn't have a lot of experience with gas tankless water heaters. He did say they lasted a long time from what he heard.
2. The original electric ones suffered from faulty components and also sucked down quite a bit of power. He was replacing his neighbors electric tankless heater and he said you could watch the meter spin when the water heater turned on (this was awhile ago before digital meters).
3. He recommends installing the biggest water heater you can and to get it from a plumbing supply store if you can and not from Lowe's. He recommends Rheem or A.O Smith brands for water heaters. He said you can get scratch and dent models for cheap, just ask the salesman if they have any in the back.
4. We install the small single sink electric water heaters here at work when we can't get hot water to that location and they don't last.
5. He recommends sticking with a tanked water heater.
I researched these years ago with my step-dad when we were replacing my mom's water heater as well as relocating it out of the laundry room to another part of the house. From what I remember, there were more website links to spare parts to fix the tankless water heaters than there were to sell them at the time. Also, I think we did some calculation and found that we needed more hot water than it could provide (3 adults in one house, clothes washer, dishwasher, etc...). So both of those things turned us off towards them.
I also helped my old boss rebuild the house he lives in now and we put in an electric tankless water heater which he ended up replacing with a regular water heater because it couldn't keep up with the demand (i.e. his wife was getting pissed that she could wash clothes, dishes and shower at the same time

).