I have the Paramount PV-3 sytem in my Shotcrete pool with Pebble -Sheen. It's 2.5 years old with no issues and it make the pool VERY low maintenance. The system does not increase back pressure as it changed circuits, it DECREASES back pressure as it hold two circuits open simultaneously during the switch. I do run higher back pressure than pools w/o in-floor, but it hasn't casued any issues to date.

I've heard reports of LONG TERM problems (20+ years) on pools with in-floor systems due to the cyclic pressure on parts of the system.

With regard to problems with the heads, that's a function of the complexity of the heads. Heads with lots of moving parts (springs, ratchets etc.) have more probems than simpler designs (like the PV-3)

Some brands of heads are VERY expensive.

AFAIK, all of the systems need the gear mechanism in the distribution valve changed every 5-10 years.

In-floor is not cheap, and adds more components to maintain, but it dramatically reduces the amount of time spent sweeping and vacuuming the pool.