Based on the description and the demos, the Rhodes is highly detailed and a leap forward from MrRay73 Mark II, not to mention more realistic than anything I've heard from the latest versions of Lounge Lizard and Pianoteq, which still don't sound convincing to me.
From the website:
"There's no keyboardist without a good Rhodes electric piano sound. And the GSi Gemini offers what can be considered the best fusion between sound fidelity and playability. This synth engine is based on more than 10 years of experience on the physical modeling simulation of a Rhodes electric piano, everything in the "body" of each single note from the attack transient to the very last decay is purely simulated. Some minor elements are added from selected sampled sources, but the most important part of the sound is pure synthesis. Every element of the mechanical piano is virtually reconstructed in the Gemini, from the hammer, the hammer-tips, the tines, the tonebars, the pick-ups, the dampers, the output filter straight to the output jack, and they all behave exactly like in the real thing. Each of the 88 notes is simulated individually, and each note is a generator on its own, thus offering the full polyphony, no note stealing and a very natural and true to the original behavior. Plus, this new simulation features a very realistic sympathetic resonance that involves the whole "harp" that can vibrate and resonate every time a key is struck. It is really hard to tell the Gemini simulation from a real Rhodes piano, the level of realism and the number of details is very high."