My mom used the Quantum 600 with power tilt, leg extension and recline. Of course, with PALS nothing ends up being the generic stock and she ended up with a combination gel seat. The tilt and recline were indispensable for her. Especially as her tailbone became closer and closer to the surface of her skin. It was the only way she was able to alleviate the pressure. When she became very thin, I did have to move her forward, squish the gel around from time to time because her tailbone would torpedo to the base of the chair!
It did a great job going over the thresholds, bumps in the lawn, etc. It would eat up throw rugs or things she drove over if it they were not nailed down.
I still can't believe how expensive these things are. It was more than $24,000. And the 600 is on the lower end of the scale! Thank goodness for health insurance. And the ALS loan closet that gave us one while we waited the 5 months for ours to come in! (And that darn chair is for sale currently, if anyone is interested. A mere $5000. I wish we could donate it, but financially that's not possible. :-(