Ruckus does two things in 2.4GHz. Obviously, there's an extra spatial stream which takes you up to 600mbit. But the new thing is 256QAM -- the 802.11ac 5GHz modulation scheme has been made available in 2.4GHz now.
This technology is marketed as "TurboQAM" in Broadcom, and has been on consumer chipsets for a long time. Anecdotally, I have noticed that at least in relatively RF-clean consumer environments, this really does work, leading to much faster apparent speeds on 2.4GHz.
Now, the interesting part is whether or not Ruckus is still using QCA chipsets in the R710, since traditionally 256QAM 2.4GHz has been Broadcom exclusive.
As far as client compatibility, I don't have a full list, but I believe most 802.11ac Broadcom chipsets support it. And Broadcom is the most popular wifi chipset vendor by a large margin.