I'd get quotes for the same pool design from another 2-3 builders. Also ask for the name and address of the last 30 pools he built and a couple of references from 5 years and 10 years back. I would not only get these references, I'd also call them. Check with the BBB and see if they have a record there.

$27,000 sounds probably right for a play pool with tanning ledge, flagstone coping and a water feature. The 400sq ft of decking is rather small, I would probably add more. The gunite warranty is nice, the fact that it's transferrable. I wonder what the 15 year warranty on the decking covers. Check what is covered and what is not. I am betting my own $500 that they will not finish the pool within 35 days from contract signing unless you're outside of city limit and they don't need permits. My builder said a typical build schedule is 40 days from dig date not counting rain delays.

On the Nature2 system, ask him if it's the Nature 2 Express or the Nature 2 Professional "G" Vessel. One costs $80 the other is $360.I asked my builder to have the Nature 2 installed and he said he'd "throw it in". Guess which one he "threw in"? You guessed it right, the cheap one. I had them upgrade it to the Express 2 Professional "G" at no additional cost.

Did you also get a salt water generator? Or is that what you meant by Nature 2? Zodiac makes a salt generator/nature2 combo unit.

Good luck!