The one I'm looking at goes to 150 degrees. It's electric. Whats wrong with electric?

You have to watch you gas piping size to ensure it would have enough volume. Check out Navien they are able to run off an existing 1/2" gas line and have a 2" pvc vent. There are also tax rebates having an energy star rating. As Slim said stay away from electric if that's what you were looking at. How many bathtubs do you have? They are the future of hot water and if properly maintained should last a lifetime. If something springs a leak or quits working it can all be replaced with a Phillips head screwdriver. As long as they keep making parts it could be your last heater to have to buy. It's a good idea to neutralize it every year and you can buy the pump and chemicals at a local supply house and watch YouTube on how to do it. It's very simple.

Location of your plumbing will make a difference on the installation price if you go tankless. It has to be vented with a stainless pipe, and have a minimum amount of clearance all the way up around the exhaust. It will be fairly easy if it is in the attic or on an outside wall. It will get pretty expensive if it is in the garage, or somewhere on the bottom floor.

Thinking about going tankless. Anybody know anything about them? Good or bad

Tankless is expensive, both for the unit and for installation. Not too bad if you get one while the house is built and you design it in, but very expensive to add down the road.