I'm starting my 4th season (3rd with my Dolphin Standard).

I have an 18x36 IG Vinyl - and I have had no problems. I love the Dolphin (or any other quality robotic I would imagine).

The only think I have observed, is that the plumbing outlets in the pool (returns, and rough in for a pressure side) cause the Dolphin to hang when 'scrubbing' the water line. This causes the Dolphin to sit 'spinning it's wheels' on that fixture, which in turn has rubbed very very small spots in the liner. All that it has done is remove the print on the liner, not actually damaged the liner, and these spots are less 1/2 an inch long, and only about 2 or 3 mm wide.

The real nice part of a Dolphin or other robotic is the ease of use. Simply unwind the cord, hook it to the power supply, plug it in the outlet, and toss it in the pool. It takes about 3 or 4 minutes to get it in the water.

8 hours later, I go get it out of the water, pull the filter bag out, and rinse it really well. I let the bag dry until it doesn't drip anymore and then take it inside to complete drying. Removing it from the water and cleaning the bag takes about 10 minutes. I usually use the bag 5 or 6 times before I toss it in the washing machine with a load of whites on warm water (no bleach).

It was well worth every penny ($799 with 20% off coupon at Leslie's Pool).

I considered the pressure side cleaners since my pool had the plumbing roughed in - but cost was virtually the same - and the extra hoses and hassle turned me off the pressure side cleaners.

Good luck - I'm sure you'll appreciate the time savings of either versus manual vacuuming and cleaning.

Oh - I almost forgot - If I had it to do over again - I would choose the Dolphin Dynamic or other 'remote control' robot due to the ability to quickly do spot cleaning of those common accumulation areas. It's an extra few hundred - but worth it versus trying to push the manual model around with the skimmer net and pole.