I've had two brands: Dolphin and Blue Diamond.
My experience with the Dolphin was that it worked GREAT for 2 seasons, then failed. I sent it back to their support company, came back just as bad. They suggested I tape lead weights to the unit...lead, in water my kids swim in. Finally they sent me a replacement unit. That worked for a season and then started giving me trouble. I finally sold it.
The Blue Diamond worked for a couple of seasons and then failed. Unlike the Dolphin, I was able to drop the unit off nearby. Rather than pick it up, they shipped it back to me ahead of schedule and it's worked ever since, 3 seasons now.
The Dolphin is "smarter" and doesn't tangle its cord on the ladder. I have to take it out every time I vacuum. But that's easy. The Diamond is much, MUCH faster (3 hrs vs 8 hrs) and has a far easier to clean bag, but it's just as effective as the Dolphin's. The remote is much cruder, but the three drive motors (left and right track, and vacuum) are 3x the size of the Dolphin's and pack more power.
For both, one cycle is like a day's worth of filtering--they pump that much water through. Since my pump is laid up for a few more days, the BD is keeping my water clear with a once-a-day run.
Is it worth it? To me it is. Is it to you? Only you can decide.