30 - 75 gallon capacities

Piezo igniter

Advanced gas valve

Available with additional foam insulation (for .62 Energy Factor needed for some rebates)

Very reliable

Lowest installed cost

Can supply multiple hot water needs simultaneously

Not highly efficient

Typical lifespan roughly 10 - 12 years

You can run the tank out of hot water (and have to wait for it to re-heat) 

Open combustion / atmospheric venting (burns indoor air with drafting effect to roof)

Some tanks can achieve the .67 Energy Factor (EF rating) needed to qualify for local rebate programs.  High efficiency models are more complex and cost considerably more to install.  Economic payback is not a strong selling point.  These tanks are ideally suited for those with strong energy conservation goals or the need to eliminate the 'drafting effect' of standard tanks.