In a word, bloody awful. I actually bought one of my own about 15 years ago. They had two of them, one in the quire and one in the nave. The instrument was a Hammond C3, with the full AGO pedalboard, two manuals, a swell pedal, enclosed speakers, and a very interesting set of pedal stops, which included not one but to 32 footers, one diapason and one reed. You could actually get a relatively good foundation tone out of it.
The manuals had drawbars and presets, which were implemented as another 'octave' at the left end of the keyboard. One key enabled the drawbars, the other had some solo combinations, including a trumpet, oboe and some flute stops. Unfortunately, no thumb pistons.
The drawbars brought out individual tones of 16', 10 2/3, 8, 5 1/3, 4, 1 1/5, 1 1/3 and 1 foot pitch, you could get a reasonable chorus out of it, but could not couple the manuals or get a reed involved as well.
Not bad for 1965 technology, mine lasted about 3 years before the main amplifier died and I could not find any replacement parts.