A few observations about the Z5 after using it a few days: I had always managed to get the pool floor "clean enough" before, but I didn't ever realize how far that was from "really clean!" This thing gets it really clean!
I've run it on three full cycles so far, and the second and third times it's picked up stuff I didn't even know was there. I've found that the 2-3 or 3-2 handle angle seems to work well, just as previous posters have said. M pool has been plagued with pollen (everything around here is caked with yellow powder this spring) and the Dolphin did a pretty respectable job of vacuuming that fine stuff up, along with earthworms, caterpillars, oak tassels, and just a bunch of crud.
It does not seem to perform as well with the fine pleated filters, and wouldn't even climb to the waterline. Maybe it's an issue of the amount of water flow through those, but it works as advertised with the standard filters. Maybe I'll reserve those for floor-only cycles where it's mostly dust and pollen.
I have two floor drains, and it never gets stuck on one of them and ALWAYS gets stuck on the other. I guess the other one must be just an 1/8" higher or something. A nudge with a brush dislodges it, but I have to kind of keep an eye on it, as it seems to head right for the problematic drain first thing.
All stored away on the caddy, it's way bigger than I envisioned, and the spot I'd planned to store it isn't going to be practical, so I'm going to rethink how to keep it handy and convenient.
The bottom line is, even though it was a lot of money, my pool has NEVER been this clean. I'm happy with the purchase and really looking forward to the rest of the season. Thanks for steering me in the right direction.