I also have a tankless. As slowguy mentions, you pretty much have instant hot water. I also know that this is not the case for most parts of the county, but down here in Texas they put water heaters in the attic to save space in the garage since we don't have basements. The idea of having a traditional water heater blow in the attic and have 50-80ish gallons of water coming through my ceiling was very nerve racking. Also a pro is the size tankless we have for the house, we can have 3 things all running at the same time and never run out (any combo of shower, tub, washing machine, dish washer). Perfect since its just the wife and I.
One big con that I experienced during the big freeze that hit us a couple months back. Since its never happened before in my lifetime, and 11 degrees for a few days changes things, a small plastic fitting inside cracked inside the unit. It leaked a bit, not much before i noticed it. Again, it only holds about 5 gallons and not 80 like a normal tank. Pretty much owner error, didn't even think to get up there to drain the unit during the freeze. Wouldn't of had to do it for a regular tank. Anyways, there was no replacement parts available so i had to replace the entire unit.
So far that was the only downfall to the unit. Obviously it was an expensive to replace, but I definitely prefer it to a traditional tank.