So, I've got the Discovery up and running now. Please keep in mind I'm a first time pool owner with no experience other than with my old Hayward Navigator suction side cleaner.
Extremely easy to assemble the cart, plug everything up and get it up and running. Probably took me 10 minutes to read the manual and get her in the water. I could see immediately how effective it was by the paths of clean bottom it left. Went up my walls a couple of times fairly easily. Seemed a little awkward to me when it gets to the top of the wall it kinda falls backwards and the floats stabilize it and then it sort of drifts back to the wall and continues cleaning. Not sure how normal that is but thought I'd mention it anyway.
Let it run its first 3 hour cycle and opened up to get the filter bag, and dang it was filled with all kinds of crud I didn't even know were in the pool. I was concerned about how difficult it would be to clean the filter bag, but I just turned it inside out, hung it over a hose reel I have and hosed it off. Couple of minutes later and it was clean! Pretty easy. They do recommend tossing them in a washing machine once every couple of months. Did a good job of picking up small leaves, some twigs, sand and bugs. After seeing all that, I'm glad that I'm catching it before it hits my sand filter. Makes a nice "pre-filter".
Remote works well. It's not like an RC car, obviously, it's a little slow responding to the commands but absolutely functional for getting any spots it might have missed in the pre-programming.
The roller brush it comes with is a "Combined Brush" for "rough ceramic surface and mosaic tiles". They do offer a "PVC Brush" for "concrete, PVC, fiberglass and liner" as well as a "Wonder Brush" for "smooth ceramics". I'm not sure if the PVC Brush would clean my plaster any better than the Combined Brush. It looks like the Wonder brush is all foam, the PVC brush is all rubber brushes and the Combined has both rubber and some foam.
Like I mentioned before, it came with a filter bag, but there is an optional filter cartridge that requires you purchase the frame to hold the filters (around $100) and you can buy replacement filter cartridges. Again, not sure the effectiveness but the filter bag seems to be working pretty well for me.
I like the extra long 60ft cable and the included cart is not heavy duty by any means, but it seems like it will hold up well.
Of course, the ultimate test will be to see how many seasons it will last but Maytronics (manufacturer of Dolphin) does have a 2 year warranty so we'll see. So far, I'm happy with the value and performance (after one day, mind).
Any questions, feel free to ask. BTW, it was $899 with cart and remote with a 10% coupon code and free shipping.